Re: [RFC 27/32] PCI/sysfs: make I/O resource depend on HAS_IOPORT
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2021-12-27 22:04:49
Also in:
linux-pci, linux-riscv, lkml
Make the subject match historical convention (capitalize "Make"). On Mon, Dec 27, 2021 at 05:43:12PM +0100, Niklas Schnelle wrote:
Exporting I/O resources only makes sense if legacy I/O spaces are supported so conditionally add them only if HAS_IOPORT is set.
IIUC, the effect of this is that the "resource%d" file for an I/O BAR still appears in /sys, but reads or writes will fail with ENXIO. Worth mentioning that in the commit log, since one could interpret the above as meaning that the "resource%d" file exists only if HAS_IOPORT is set. I think I will *exist* but not be very useful. I also wonder what this looks like in the sysfs "resource" file and via lspci. I suppose it's useful if lspci shows the fact that the BAR exists and is an I/O BAR, even if the arch doesn't set HAS_IOPORT.
quoted hunk ↗ jump to hunk
Co-developed-by: Arnd Bergmann <arnd@kernel.org> Signed-off-by: Arnd Bergmann <arnd@kernel.org> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> --- drivers/pci/pci-sysfs.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index cfe2f85af09e..a59a85593972 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c@@ -1099,6 +1099,7 @@ static int pci_mmap_resource_wc(struct file *filp, struct kobject *kobj, return pci_mmap_resource(kobj, attr, vma, 1); } +#ifdef CONFIG_HAS_IOPORT static ssize_t pci_resource_io(struct file *filp, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count, bool write)@@ -1157,6 +1158,21 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj, return pci_resource_io(filp, kobj, attr, buf, off, count, true); } +#else +static ssize_t pci_read_resource_io(struct file *filp, struct kobject *kobj, + struct bin_attribute *attr, char *buf, + loff_t off, size_t count) +{ + return -ENXIO; +}
I assume the sysfs infrastructure prevents or fails reads/write if
res_attr->read and res_attr->write are not set at all, so maybe we
wouldn't need the stubs if we did something like this?
if (pci_resource_flags(pdev, num) & IORESOURCE_IO) {
#ifdef CONFIG_HAS_IOPORT
res_attr->read = pci_read_resource_io;
res_attr->write = pci_write_resource_io;
...
#endif
} else {
+static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf,
+ loff_t off, size_t count)
+{
+ return -ENXIO;
+}
+#endif
/**
* pci_remove_resource_files - cleanup resource files
--
2.32.0