On Mon, Aug 24, 2015 at 12:09 PM, Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx> wrote: >>> commit 84cfb2213cd400fef227ec0d7829ec4e12895da9 >>> Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> >>> Date: Thu Aug 13 19:49:52 2015 -0500 >>> >>> ACPI / scan: Rename acpi_check_dma() to acpi_dma_is_coherent() >>> >>> The name "acpi_check_dma()" doesn't give any much indication about >>> what >>> exactly it checks. The function also returns information both as a >>> normal >>> return value and as the "bool *coherent" return parameter. But >>> "*coherent" >>> doesn't actually give any extra information: it is unchanged when >>> returning >>> false and set to true when returning true. >>> >>> Rename acpi_check_dma() to acpi_dma_is_coherent() so the callers >>> read more >>> naturally. Drop the return parameter and just use the function >>> return >>> value. >>> >>> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > > This was because, at one point, we wanted to be able to differentiate > between the case _CCA=0 and missing _CCA in ARM64, where we would support > DMA (using arch-specific cache maintenance) if _CCA=0, and disable DMA when > missing _CCA on ARM64. > > It seems like the logic is now required (please see > https://www.mail-archive.com/linux-usb@xxxxxxxxxxxxxxx/msg62735.html). So, > we would need the true/false return, and the coherent variable to be able to > differentiate between the two cases. > > Please let me know what you think. It's hard for me to comment without seeing the actual patches. I think returning two values (_CCA-seen and coherent) is a confusing interface. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
