[PATCH v6 3/6] PCI/ATS: Mandate checking pci_ats_supported() before pci_prepare_ats()

[Nicolin Chen]

On Fri, May 29, 2026 at 11:12:05AM +0000, Pranjal Shrivastava wrote:
> Currently, pci_prepare_ats() internally calls pci_ats_supported() and
> returns -EINVAL if the device does not support ATS. While this provides
> a silent safety check, it conflates support detection with configuration.
> 
> Update pci_prepare_ats() to wrap the internal pci_ats_supported check in
> a WARN_ON(). This mandates all callers to call pci_prepare_ats() only if
> the function supports ATS.
> 
> Update the function documentation to mention that callers must verify
> ATS support (via pci_ats_supported()) before calling pci_prepare_ats().
> 
> Suggested-by: Baolu Lu <baolu.lu at linux.intel.com>
> Signed-off-by: Pranjal Shrivastava <praan at google.com>

Sashiko pointed out a bisect issue. So, you might want to reorder
a bit. The patch itself looks good to me.

Reviewed-by: Nicolin Chen <nicolinc at nvidia.com>