Alan Cox wrote: > On Thu, 29 Nov 2007 23:33:36 +0900 > Tejun Heo <htejun@xxxxxxxxx> wrote: > >> ATAPI DMA is filled with mines. Sector aligned READ transfers usually >> work but many other commands transfer non-sector aligned or variable >> number of bytes, and there are devices and controllers which have >> problems dealing with such non-aligned DMA transactions. >> >> This patch implement ATAPI per-command-type DMA horkages and EH logic >> to set those quickly. This way, failures localized to certain command >> type don't affect other operations (most importantly READs) and >> working configuration is found quickly such that the device can be >> used. > > This I think makes sense. We want to fail rapidly when we discover DMA > problems with ATAPI and non core commands. OTOH we want to be pretty > resistant to randomly dropping into PIO on stuff we know works reliably. > >> + ATAPI_DMA_HORKAGE_WRITE = (1 << 28), /* PIO for WRITEs */ >> + ATAPI_DMA_HORKAGE_READ_CD = (1 << 29), /* PIO for READ_CDs */ >> + ATAPI_DMA_HORKAGE_READ_DVD_STR = (1 << 30), /* PIO for READ DVD STR */ >> + ATAPI_DMA_HORKAGE_MISC = (1 << 31), /* PIO for MISC commands */ >> + >> /* DMA mask for user DMA control: User visible values; DO NOT >> renumber */ >> ATA_DMA_MASK_ATA = (1 << 0), /* DMA on ATA Disk */ > > What are the locking rules for ->horkage at this point ? It's owned by EH. Only EH sets it. -- tejun - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
