Re: [PATCH] PCI : check if type 0 devices have all BARs of size zero
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2021-02-15 21:13:46
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On Fri, Feb 12, 2021 at 11:08:56AM +0100, Wasim Khan wrote:
From: Wasim Khan <redacted> Log a message if all BARs of type 0 devices are of size zero. This can help detecting type 0 devices not reporting BAR size correctly.
I could be missing something, but I don't think we can do this. I would think the simplest possible presilicon testing would find errors like this, and the first attempt to have a driver claim the device would fail if required BARs were missing, so I'm not sure what this would add. While the subject line says "type 0 devices," this code path is also used for type 1 devices (bridges), and it's quite common for bridges to have no BARs, which means they would all be hardwired to zero. It is also legal for even type 0 devices to implement no BARs. They may be operated entirely via config space or via device-specific BARs that are unknown to the PCI core.
quoted hunk ↗ jump to hunk
Signed-off-by: Wasim Khan <redacted> --- drivers/pci/probe.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 953f15abc850..6438d6d56777 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c@@ -321,6 +321,7 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type, static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom) { unsigned int pos, reg; + bool found = false; if (dev->non_compliant_bars) return;@@ -333,8 +334,12 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom) struct resource *res = &dev->resource[pos]; reg = PCI_BASE_ADDRESS_0 + (pos << 2); pos += __pci_read_base(dev, pci_bar_unknown, res, reg); + found |= res->flags ? 1 : 0; } + if (!dev->hdr_type && !found) + pci_info(dev, "BAR size is 0 for BAR[0..%d]\n", howmany - 1); + if (rom) { struct resource *res = &dev->resource[PCI_ROM_RESOURCE]; dev->rom_base_reg = rom;-- 2.25.1