Re: [PATCH v3 1/2] PCI: endpoint: pci-epf-test: Add support for capabilities

[Niklas Cassel <cassel@kernel.org>]

Hello Bjorn,

On Sat, Jan 18, 2025 at 02:34:21PM -0600, Bjorn Helgaas wrote:
> On Tue, Dec 03, 2024 at 07:38:53AM +0100, Niklas Cassel wrote:
> > The test BAR is on the EP side is allocated using pci_epf_alloc_space(),
> > which allocates the backing memory using dma_alloc_coherent(), which will
> > return zeroed memory regardless of __GFP_ZERO was set or not.
> 
> > +static void pci_epf_test_set_capabilities(struct pci_epf *epf)
> > +{
> > +	struct pci_epf_test *epf_test = epf_get_drvdata(epf);
> > +	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
> > +	struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
> > +	struct pci_epc *epc = epf->epc;
> > +	u32 caps = 0;
> > +
> > +	if (epc->ops->align_addr)
> > +		caps |= CAP_UNALIGNED_ACCESS;
> > +
> > +	reg->caps = cpu_to_le32(caps);
> 
> "make C=2 drivers/pci/" complains about this:
> 
>   drivers/pci/endpoint/functions/pci-epf-test.c:756:19: warning: incorrect type in assignment (different base types)
>   drivers/pci/endpoint/functions/pci-epf-test.c:756:19:    expected unsigned int [usertype] caps
>   drivers/pci/endpoint/functions/pci-epf-test.c:756:19:    got restricted __le32 [usertype]

Yes, pci-epf-test is broken when it comes to endianness, as reported here:
https://lore.kernel.org/linux-pci/ZxYHoi4mv-4eg0TK@ryzen.lan/


Nice to see that sparse is complaining about it! :)

Mani said that he was going to work on it, but I guess that it fell through
the cracks.

I sent patch for it here:
https://lore.kernel.org/linux-pci/20250120115009.2748899-2-cassel@kernel.org/T/#u

FWIW, I tested it on rk3588 which is little-endian, and that still worked.

However, if you feel that it is a bit too late to queue it now, you could
also take only the following change from the patch above:

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index ffb534a8e50a..cb7e57377214 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -76,7 +76,7 @@ struct pci_epf_test_reg {
        u32     irq_type;
        u32     irq_number;
        u32     flags;
-       u32     caps;
+       __le32  caps;
 } __packed;
 
 static struct pci_epf_header test_header = {


Kind regards,
Niklas