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SubjectRe: [PATCH v10 4/8] PCI/sysfs: Allow userspace to query and set device reset mechanism
On 21/07/27 06:28PM, Bjorn Helgaas wrote:
> On Fri, Jul 09, 2021 at 06:08:09PM +0530, Amey Narkhede wrote:
> > Add reset_method sysfs attribute to enable user to query and set user
> > preferred device reset methods and their ordering.
> >
> > Co-developed-by: Alex Williamson <alex.williamson@redhat.com>
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
> > ---
> > Documentation/ABI/testing/sysfs-bus-pci | 19 +++++
> > drivers/pci/pci-sysfs.c | 103 ++++++++++++++++++++++++
> > 2 files changed, 122 insertions(+)
> >
[...]

> > + if (i == PCI_NUM_RESET_METHODS) {
> > + kfree(options);
> > + return -EINVAL;
> > + }
> > + }
> > +
> > + if (!pci_reset_fn_methods[1].reset_fn(pdev, 1) && reset_methods[0] != 1)
> > + pci_warn(pdev, "Device specific reset disabled/de-prioritized by user");
>
> Hmmm. I sort of see the point here, but I wish we didn't have the
> implicit dependency on pci_reset_fn_methods[1] being
> pci_dev_specific_reset().
>
> I know we've talked about this before. I'm still not 100% sure either
> of these warnings is worthwhile, especially since we're not *using*
> the reset here. It might be useful at the point where we try to *do*
> a reset. I dunno. Maybe this is the best place since this is where
> the user potentially screwed up.
>
I agree this is the best place for the warning as this where potentially
broken reset methods may get called/prioritized. We can move this check
to __pci_reset_function_locked() if you want.

> > +set_reset_methods:
> > + memcpy(pdev->reset_methods, reset_methods, sizeof(reset_methods));
> > + kfree(options);
> > + return count;
> > +}
> > +static DEVICE_ATTR_RW(reset_method);
> > +
> > +static struct attribute *pci_dev_reset_method_attrs[] = {
> > + &dev_attr_reset_method.attr,
> > + NULL,
> > +};
> > +
> > +static umode_t pci_dev_reset_method_attr_is_visible(struct kobject *kobj,
> > + struct attribute *a, int n)
> > +{
> > + struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
> > +
> > + if (!pci_reset_supported(pdev))
> > + return 0;
> > +
> > + return a->mode;
> > +}
> > +
> > +static const struct attribute_group pci_dev_reset_method_attr_group = {
> > + .attrs = pci_dev_reset_method_attrs,
> > + .is_visible = pci_dev_reset_method_attr_is_visible,
> > +};
> > +
> > static ssize_t reset_store(struct device *dev, struct device_attribute *attr,
> > const char *buf, size_t count)
> > {
> > @@ -1491,6 +1593,7 @@ const struct attribute_group *pci_dev_groups[] = {
> > &pci_dev_config_attr_group,
> > &pci_dev_rom_attr_group,
> > &pci_dev_reset_attr_group,
> > + &pci_dev_reset_method_attr_group,
> > &pci_dev_vpd_attr_group,
> > #ifdef CONFIG_DMI
> > &pci_dev_smbios_attr_group,
> > --
> > 2.32.0
> >

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