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