Messages in this thread | | | Date | Wed, 07 May 2014 21:15:39 +0200 | From | Lars-Peter Clausen <> | Subject | Re: [PATCH v1 3/3] dma: tegra: avoid int overflow for transferred count |
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On 05/07/2014 06:38 PM, Stephen Warren wrote: > On 05/06/2014 03:22 PM, Christopher Freeman wrote: >> bytes_transferred will overflow during long audio playbacks. Since >> the driver only ever consults this value modulo bytes_requested, store the >> value modulo bytes_requested. > > The audio driver may only interpret the value modulo bytes_requested, > but what about other drivers such as the high-speed UART (and SPI?) drivers? > > What is the dmaengine API's design requirement here, and what do other > dmaengine drivers do. If it's to store the modulo, then I'm fine with > this change.
Yep, this part of the API. The residue should be between transfer length and 0. While 0 is special and should only be returned if the transfer has finished. For cyclic transfers this means it should never be zero. So if transferred_bytes is incremented modulo length and residue is length - transferred_bytes you get the correct result.
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