nvmem: rmem: Fix return value of rmem_read()

commit 28b008751aa295612318a0fbb2f22dd4f6a83139 upstream.

reg_read() callback registered with nvmem core expects 0 on success and
a negative value on er

nvmem: rmem: Fix return value of rmem_read()

commit 28b008751aa295612318a0fbb2f22dd4f6a83139 upstream.

reg_read() callback registered with nvmem core expects 0 on success and
a negative value on error but rmem_read() returns the number of bytes
read which is treated as an error at the nvmem core.

This does not break when rmem is accessed using sysfs via
bin_attr_nvmem_read()/write() but causes an error when accessed from
places like nvmem_access_with_keepouts(), etc.

Change to return 0 on success and error in case
memory_read_from_buffer() returns an error or -EIO if bytes read do not
match what was requested.

Fixes: 5a3fa75a4d9c ("nvmem: Add driver to expose reserved memory as nvmem")
Cc: stable@vger.kernel.org
Signed-off-by: Joy Chakraborty <joychakr@google.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240628113704.13742-2-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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nvmem: rmem: Use NVMEM_DEVID_AUTO

It is reasonable to declare multiple nvmem blocks. Unless a unique 'id'
is passed in for each block there may be name clashes.

Avoid this by using the magic token

nvmem: rmem: Use NVMEM_DEVID_AUTO

It is reasonable to declare multiple nvmem blocks. Unless a unique 'id'
is passed in for each block there may be name clashes.

Avoid this by using the magic token NVMEM_DEVID_AUTO.

Fixes: 5a3fa75a4d9c ("nvmem: Add driver to expose reserved memory as nvmem")
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Signed-off-by: Ivan T. Ivanov <iivanov@suse.de>
Reviewed-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Message-ID: <20230611140330.154222-6-srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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nvmem: rmem: Fix return value check in rmem_read()

In case of error, the function memremap() returns NULL pointer
not ERR_PTR(). The IS_ERR() test in the return value check
should be replaced with N

nvmem: rmem: Fix return value check in rmem_read()

In case of error, the function memremap() returns NULL pointer
not ERR_PTR(). The IS_ERR() test in the return value check
should be replaced with NULL test.

Fixes: 5a3fa75a4d9c ("nvmem: Add driver to expose reserved memory as nvmem")
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221118063840.6357-3-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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nvmem: Add driver to expose reserved memory as nvmem

Firmware/co-processors might use reserved memory areas in order to pass
data stemming from an nvmem device otherwise non accessible to Linux.
For

nvmem: Add driver to expose reserved memory as nvmem

Firmware/co-processors might use reserved memory areas in order to pass
data stemming from an nvmem device otherwise non accessible to Linux.
For example an EEPROM memory only physically accessible to firmware, or
data only accessible early at boot time.

In order to expose this data to other drivers and user-space, the driver
models the reserved memory area as an nvmem device.

Tested-by: Tim Gover <tim.gover@raspberrypi.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20210129171430.11328-5-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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