On Wed, 14 Jul 2021 at 17:51, Marek Behún marek.behun@nic.cz wrote:
The _erase() method of the mtdpart driver, part_erase(), currently implements offset shifting (for given mtdpart partition) in a weird way:
- part_erase() adds partition offset to block address
- parent driver's _erase() method is called
- parent driver's _erase() method calls mtd_erase_callback()
- mtd_erase_callback() subtracts partition offset from block address so that the callback function is given correct address
The problem here is that if the parent's driver does not call mtd_erase_callback() in some scenario (this was recently a case for spi_nor_erase(), which did not call mtd_erase_callback() at all), the offset is not shifted back.
Moreover the code would be more readable if part_erase() not only added partition offset before calling parent's _erase(), but also subtracted it back afterwards. Currently the mtd_erase_callback() is expected to do this subtracting since it does have to do it anyway.
Add the more steps to this procedure: 5. mtd_erase_callback() adds partition offset to block address so that it returns the the erase_info structure members as it received them 6. part_erase() subtracts partition offset from block address
This makes the code more logical and also prevents errors in case parent's driver does not call mtd_erase_callback() for some reason.
(BTW, the purpose of mtd_erase_callback() in Linux is to inform the caller that it is done, since in Linux erasing is done asynchronously. We are abusing the purpose of mtd_erase_callback() in U-Boot for completely different purpose. The callback function itself has empty implementation in all cases in U-Boot.)
Signed-off-by: Marek Behún marek.behun@nic.cz Tested-by: Masami Hiramatsu masami.hiramatsu@linaro.org
drivers/mtd/mtdpart.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-)Reviewed-by: Simon Glass sjg@chromium.org
Reviewed-by: Simon Glass sjg@chromium.org