08.02.2019 20:53, Sowjanya Komatineni пишет: >>>>>> >>>>>>> I'm still also suggesting to squash "fix maximum transfer size" into >>>>>>> this patch because it is really part of DMA-support enabling. >>>>>> >>>>>> Max transfer length limits apply to PIO also but for DMA its more needed >>>>>> to prevent crash. >>>>>> So had this as patch before DMA as its applicable for both DMA & PIO. >>>>> >>>>> Oh, so the packet_header size also shall be excluded for the PIO as well, >>>>> really? It looked to me that PIO doesn't have that restriction and we >>>>> only need to exclude the header size for DMA.. >>>>> >>>>>> We exchanged on this yesterday, so thought the reason you want to squash >>>>>> separate patch and include in this is due to max msg len limit and when >>>>>> moved into hw feature. >>>>> >>>>> If PIO limits are incorrect, then it's absolutely fine to do it in the >>>>> separate patch. I probably just misunderstood your point. >>>>> >>>>>> Sorry should have verified before sending. Please confirm if I leave max >>>>>> transfer as separate patch or add to this DMA support. Will update along >>>>>> with dma buf size fix. >>>>>> >>>>>> But max transfer limit applied to PIO also and that’s why added it >>>>>> before DMA patch to show its dependency >>>>>> >>>>> >>>>> And then you need to explicitly tell in the commit message that PIO >>>>> limits are incorrect. >>>> Commit message says Tegra I2C max limit per packets transfer meaning >>>> that’s interface transfer limit so applies to both PIO & DMA. >>>> Will add explicitly indicating applicable for both PIO & DMA to be more >>>> clear >>> >>> Thank you. >>> >>>>> >>>>> It also probably worth to add a stable-tag to the commit message to >>>>> request backporting of the limits-fixing patch to the stable kernels: >>>>> >>>>> Cc: [email protected] >>>>> >>>> Sorry I am new to upstream submissions. By adding stable-tag to commit >>>> message, do you mean explicitly mentioning this patch applicable to old >>>> kernel and adding in patch CC [email protected]? >>>> >>> >>> You just need to add "Cc: [email protected]" to the commit message, >>> like you did for the "Reviewed-by:". Don't add "[email protected]" to >>> the email recipients. See for example [0]. >>> >>> [0] https://lore.kernel.org/patchwork/patch/1001991/ >>> >> >> And yes, it will mean that patch is applicable for older kernels. > > Thanks Dmitry. Added Cc: [email protected] > Also has to use 65535 instead of 64K because when buf size is computed using > max_write_len with addition of packet header it will be exact 64K but max msg > len is 65535 > So 1 byte less 64K should be OK
It is absolutely fine for dma_buf size to be larger than the message len. The max_write_len is off by one byte from the correct value by using 65535 - PACKET_HEADER_SIZE, I'd recommend to keep the SZ_64K.
