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308 lines
9.6 KiB
Diff
308 lines
9.6 KiB
Diff
From 8dc0b1158dcffd78ea2b3a5604b82ee826de687b Mon Sep 17 00:00:00 2001
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From: Zhanyong Wang <zhanyong.wang@mediatek.com>
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Date: Mon, 8 Nov 2021 13:58:51 +0800
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Subject: [PATCH 1/5] nvmem: core: Add functions to make number reading easy
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Sometimes the clients of nvmem just want to get a number out of
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nvmem. They don't want to think about exactly how many bytes the nvmem
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cell took up. They just want the number. Let's make it easy.
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In general this concept is useful because nvmem space is precious and
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usually the fewest bits are allocated that will hold a given value on
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a given system. However, even though small numbers might be fine on
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one system that doesn't mean that logically the number couldn't be
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bigger. Imagine nvmem containing a max frequency for a component. On
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one system perhaps that fits in 16 bits. On another system it might
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fit in 32 bits. The code reading this number doesn't care--it just
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wants the number.
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We'll provide two functions: nvmem_cell_read_variable_le_u32() and
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nvmem_cell_read_variable_le_u64().
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Comparing these to the existing functions like nvmem_cell_read_u32():
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* These new functions have no problems if the value was stored in
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nvmem in fewer bytes. It's OK to use these function as long as the
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value stored will fit in 32-bits (or 64-bits).
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* These functions avoid problems that the earlier APIs had with bit
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offsets. For instance, you can't use nvmem_cell_read_u32() to read a
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value has nbits=32 and bit_offset=4 because the nvmem cell must be
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at least 5 bytes big to hold this value. The new API accounts for
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this and works fine.
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* These functions make it very explicit that they assume that the
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number was stored in little endian format. The old functions made
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this assumption whenever bit_offset was non-zero (see
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nvmem_shift_read_buffer_in_place()) but didn't whenever the
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bit_offset was zero.
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NOTE: it's assumed that we don't need an 8-bit or 16-bit version of
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this function. The 32-bit version of the function can be used to read
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8-bit or 16-bit data.
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At the moment, I'm only adding the "unsigned" versions of these
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functions, but if it ends up being useful someone could add a "signed"
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version that did 2's complement sign extension.
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At the moment, I'm only adding the "little endian" versions of these
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functions. Adding the "big endian" version would require adding "big
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endian" support to nvmem_shift_read_buffer_in_place().
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Signed-off-by: Douglas Anderson <dianders@chromium.org>
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Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
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Link: https://lore.kernel.org/r/20210330111241.19401-7-srinivas.kandagatla@linaro.org
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
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Signed-off-by: Zhanyong Wang <zhanyong.wang@mediatek.com>
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Change-Id: I3e1d96ec1680812d5e24681c79852c9b36899559
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---
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drivers/nvmem/core.c | 161 +++++++++++++++++++++++++++------
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include/linux/nvmem-consumer.h | 15 +++
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2 files changed, 150 insertions(+), 26 deletions(-)
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diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
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index c0f4324d8f7c..e26b25b5c288 100644
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--- a/drivers/nvmem/core.c
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+++ b/drivers/nvmem/core.c
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@@ -1102,16 +1102,8 @@ int nvmem_cell_write(struct nvmem_cell *cell, void *buf, size_t len)
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}
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EXPORT_SYMBOL_GPL(nvmem_cell_write);
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-/**
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- * nvmem_cell_read_u16() - Read a cell value as an u16
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- *
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- * @dev: Device that requests the nvmem cell.
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- * @cell_id: Name of nvmem cell to read.
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- * @val: pointer to output value.
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- *
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- * Return: 0 on success or negative errno.
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- */
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-int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val)
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+static int nvmem_cell_read_common(struct device *dev, const char *cell_id,
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+ void *val, size_t count)
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{
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struct nvmem_cell *cell;
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void *buf;
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@@ -1126,21 +1118,50 @@ int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val)
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nvmem_cell_put(cell);
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return PTR_ERR(buf);
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}
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- if (len != sizeof(*val)) {
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+ if (len != count) {
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kfree(buf);
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nvmem_cell_put(cell);
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return -EINVAL;
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}
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- memcpy(val, buf, sizeof(*val));
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+ memcpy(val, buf, count);
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kfree(buf);
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nvmem_cell_put(cell);
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return 0;
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}
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+
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+/**
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+ * nvmem_cell_read_u8() - Read a cell value as a u8
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+ *
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+ * @dev: Device that requests the nvmem cell.
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+ * @cell_id: Name of nvmem cell to read.
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+ * @val: pointer to output value.
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+ *
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+ * Return: 0 on success or negative errno.
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+ */
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+int nvmem_cell_read_u8(struct device *dev, const char *cell_id, u8 *val)
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+{
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+ return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
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+}
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+EXPORT_SYMBOL_GPL(nvmem_cell_read_u8);
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+
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+/**
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+ * nvmem_cell_read_u16() - Read a cell value as a u16
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+ *
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+ * @dev: Device that requests the nvmem cell.
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+ * @cell_id: Name of nvmem cell to read.
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+ * @val: pointer to output value.
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+ *
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+ * Return: 0 on success or negative errno.
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+ */
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+int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val)
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+{
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+ return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
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+}
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EXPORT_SYMBOL_GPL(nvmem_cell_read_u16);
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/**
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- * nvmem_cell_read_u32() - Read a cell value as an u32
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+ * nvmem_cell_read_u32() - Read a cell value as a u32
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*
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* @dev: Device that requests the nvmem cell.
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* @cell_id: Name of nvmem cell to read.
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@@ -1149,32 +1170,120 @@ EXPORT_SYMBOL_GPL(nvmem_cell_read_u16);
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* Return: 0 on success or negative errno.
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*/
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int nvmem_cell_read_u32(struct device *dev, const char *cell_id, u32 *val)
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+{
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+ return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
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+}
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+EXPORT_SYMBOL_GPL(nvmem_cell_read_u32);
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+
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+/**
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+ * nvmem_cell_read_u64() - Read a cell value as a u64
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+ *
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+ * @dev: Device that requests the nvmem cell.
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+ * @cell_id: Name of nvmem cell to read.
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+ * @val: pointer to output value.
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+ *
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+ * Return: 0 on success or negative errno.
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+ */
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+int nvmem_cell_read_u64(struct device *dev, const char *cell_id, u64 *val)
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+{
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+ return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val));
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+}
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+EXPORT_SYMBOL_GPL(nvmem_cell_read_u64);
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+
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+static const void *nvmem_cell_read_variable_common(struct device *dev,
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+ const char *cell_id,
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+ size_t max_len, size_t *len)
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{
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struct nvmem_cell *cell;
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+ int nbits;
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void *buf;
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- size_t len;
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cell = nvmem_cell_get(dev, cell_id);
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if (IS_ERR(cell))
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- return PTR_ERR(cell);
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+ return cell;
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- buf = nvmem_cell_read(cell, &len);
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- if (IS_ERR(buf)) {
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- nvmem_cell_put(cell);
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- return PTR_ERR(buf);
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- }
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- if (len != sizeof(*val)) {
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+ nbits = cell->nbits;
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+ buf = nvmem_cell_read(cell, len);
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+ nvmem_cell_put(cell);
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+ if (IS_ERR(buf))
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+ return buf;
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+
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+ /*
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+ * If nbits is set then nvmem_cell_read() can significantly exaggerate
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+ * the length of the real data. Throw away the extra junk.
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+ */
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+ if (nbits)
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+ *len = DIV_ROUND_UP(nbits, 8);
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+
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+ if (*len > max_len) {
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kfree(buf);
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- nvmem_cell_put(cell);
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- return -EINVAL;
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+ return ERR_PTR(-ERANGE);
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}
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- memcpy(val, buf, sizeof(*val));
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+
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+ return buf;
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+}
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+
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+/**
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+ * nvmem_cell_read_variable_le_u32() - Read up to 32-bits of data as a little endian number.
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+ *
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+ * @dev: Device that requests the nvmem cell.
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+ * @cell_id: Name of nvmem cell to read.
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+ * @val: pointer to output value.
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+ *
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+ * Return: 0 on success or negative errno.
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+ */
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+int nvmem_cell_read_variable_le_u32(struct device *dev, const char *cell_id,
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+ u32 *val)
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+{
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+ size_t len;
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+ const u8 *buf;
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+ int i;
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+
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+ buf = nvmem_cell_read_variable_common(dev, cell_id, sizeof(*val), &len);
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+ if (IS_ERR(buf))
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+ return PTR_ERR(buf);
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+
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+ /* Copy w/ implicit endian conversion */
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+ *val = 0;
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+ for (i = 0; i < len; i++)
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+ *val |= buf[i] << (8 * i);
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kfree(buf);
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- nvmem_cell_put(cell);
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+
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return 0;
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}
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-EXPORT_SYMBOL_GPL(nvmem_cell_read_u32);
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+EXPORT_SYMBOL_GPL(nvmem_cell_read_variable_le_u32);
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+
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+/**
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+ * nvmem_cell_read_variable_le_u64() - Read up to 64-bits of data as a little endian number.
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+ *
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+ * @dev: Device that requests the nvmem cell.
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+ * @cell_id: Name of nvmem cell to read.
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+ * @val: pointer to output value.
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+ *
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+ * Return: 0 on success or negative errno.
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+ */
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+int nvmem_cell_read_variable_le_u64(struct device *dev, const char *cell_id,
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+ u64 *val)
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+{
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+ size_t len;
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+ const u8 *buf;
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+ int i;
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+
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+ buf = nvmem_cell_read_variable_common(dev, cell_id, sizeof(*val), &len);
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+ if (IS_ERR(buf))
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+ return PTR_ERR(buf);
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+
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+ /* Copy w/ implicit endian conversion */
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+ *val = 0;
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+ for (i = 0; i < len; i++)
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+ *val |= (uint64_t)buf[i] << (8 * i);
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+
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+ kfree(buf);
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+
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+ return 0;
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+}
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+EXPORT_SYMBOL_GPL(nvmem_cell_read_variable_le_u64);
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/**
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* nvmem_device_cell_read() - Read a given nvmem device and cell
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diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h
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index 5c17cb733224..e328c0f7eef3 100644
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--- a/include/linux/nvmem-consumer.h
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+++ b/include/linux/nvmem-consumer.h
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@@ -63,6 +63,10 @@ void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len);
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int nvmem_cell_write(struct nvmem_cell *cell, void *buf, size_t len);
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int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val);
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int nvmem_cell_read_u32(struct device *dev, const char *cell_id, u32 *val);
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+int nvmem_cell_read_variable_le_u32(struct device *dev, const char *cell_id,
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+ u32 *val);
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+int nvmem_cell_read_variable_le_u64(struct device *dev, const char *cell_id,
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+ u64 *val);
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/* direct nvmem device read/write interface */
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struct nvmem_device *nvmem_device_get(struct device *dev, const char *name);
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@@ -134,6 +138,17 @@ static inline int nvmem_cell_read_u32(struct device *dev,
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{
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return -EOPNOTSUPP;
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}
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+static inline int nvmem_cell_read_variable_le_u32(struct device *dev,
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+ const char *cell_id, u32 *val)
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+{
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+ return -ENOSYS;
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+}
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+
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+static inline int nvmem_cell_read_variable_le_u64(struct device *dev,
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+ const char *cell_id, u64 *val);
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+{
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+ return -ENOSYS;
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+}
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static inline struct nvmem_device *nvmem_device_get(struct device *dev,
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const char *name)
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--
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2.18.0
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