On Wednesday, August 26, 2015 09:00:23 AM Suravee Suthikulpanit wrote:
> Hi Rafael,
>
> On 8/26/15 06:48, Rafael J. Wysocki wrote:
>
> >[...]
> > On Wednesday, August 26, 2015 12:33:27 AM Suravee Suthikulpanit wrote:
> >> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
> >> index b9657af..55cf916 100644
> >> --- a/drivers/acpi/glue.c
> >> +++ b/drivers/acpi/glue.c
> >> @@ -168,7 +168,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
> >> struct list_head *physnode_list;
> >> unsigned int node_id;
> >> int retval = -EINVAL;
> >> - bool coherent;
> >> + int coherent;
> >
> > enum, anyone? With clearly defined values?
>
> Originally I had defined
>
> enum acpi_dma_coherency {
> ACPI_DMA_NON_COHERENT,
> ACPI_DMA_COHERENT,
> APCI_DMA_NOT_SUPPORTED = -1,
> };
>
> Although, this would need to be defined in the include/linux/acpi.h, and
> will be used also for #ifndef CONFIG_ACPI code to return errors. I was
> not sure if this would be too much. If this is preferred, I'll add this
> back in.
>
> >>
> >> if (has_acpi_companion(dev)) {
> >> if (acpi_dev) {
> >> @@ -225,7 +225,8 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
> >> if (!has_acpi_companion(dev))
> >> ACPI_COMPANION_SET(dev, acpi_dev);
> >>
> >> - if (acpi_check_dma(acpi_dev, &coherent))
> >> + coherent = acpi_check_dma_coherency(acpi_dev);
> >> + if (coherent != -1)
> >
> > Like here I'm not sure why -1 is special?
>
> It's just another value to communicate that DMA is not supported. :)
OK
So maybe use 0/1 for the coherence thing and a proper error code
(-ENOTSUPP seems to be a good candidate) for the "no DMA" case?
Then, if you rename the local variable to something like "ret",
it will be slightly less confusing.
And instead of checking against a specific negative value, you can
simply use "if (stuff < 0)" or "if (stuff >= 0)" to check whether or
not it is supported at all.
Thanks,
Rafael
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