On Tue, Jun 08, 2021 at 11:18:53AM +0530, Amey Narkhede wrote:
> Add reset_method sysfs attribute to enable user to
> query and set user preferred device reset methods and
> their ordering.
Rewrap to fill 75 columns (also apply to other patches if applicable,
e.g., 3/8 looks like it could use it).
2/8 looks like it's missing a blank line between paragraphs.
> Co-developed-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Signed-off-by: Amey Narkhede <ameynarkhede03@xxxxxxxxx>
> ---
> Documentation/ABI/testing/sysfs-bus-pci | 16 ++++
> drivers/pci/pci-sysfs.c | 118 ++++++++++++++++++++++++
> 2 files changed, 134 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index ef00fada2..cf6dbbb3c 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -121,6 +121,22 @@ Description:
> child buses, and re-discover devices removed earlier
> from this part of the device tree.
>
> +What: /sys/bus/pci/devices/.../reset_method
> +Date: March 2021
> +Contact: Amey Narkhede <ameynarkhede03@xxxxxxxxx>
> +Description:
> + Some devices allow an individual function to be reset
> + without affecting other functions in the same slot.
> + For devices that have this support, a file named reset_method
> + will be present in sysfs. Reading this file will give names
> + of the device supported reset methods and their ordering.
> + Writing the name or comma separated list of names of any of
> + the device supported reset methods to this file will set the
> + reset methods and their ordering to be used when resetting
> + the device. Writing empty string to this file will disable
> + ability to reset the device and writing "default" will return
> + to the original value.
Rewrap to fill or add a blank line if "For devices ..." is supposed to
start a new paragraph.
My guess is you intend reading to show the *currently enabled* reset
methods, not the entire "supported" set? So if a user has disabled
one of them, it no longer appears when you read the file?
> +
> What: /sys/bus/pci/devices/.../reset
> Date: July 2009
> Contact: Michael S. Tsirkin <mst@xxxxxxxxxx>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 316f70c3e..52def79aa 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1334,6 +1334,123 @@ static const struct attribute_group pci_dev_rom_attr_group = {
> .is_bin_visible = pci_dev_rom_attr_is_visible,
> };
>
> +static ssize_t reset_method_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> + ssize_t len = 0;
> + int i, prio;
> +
> + for (prio = PCI_RESET_METHODS_NUM; prio; prio--) {
> + for (i = 0; i < PCI_RESET_METHODS_NUM; i++) {
> + if (prio == pdev->reset_methods[i]) {
> + len += sysfs_emit_at(buf, len, "%s%s",
> + len ? "," : "",
> + pci_reset_fn_methods[i].name);
> + break;
> + }
> + }
> +
> + if (i == PCI_RESET_METHODS_NUM)
> + break;
> + }
I'm guessing that if you adopt the alternate reset_methods[] encoding,
this nested loop becomes a single loop and "prio" goes away?
> + if (len)
> + len += sysfs_emit_at(buf, len, "\n");
> +
> + return len;
> +}
> +
> +static ssize_t reset_method_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + u8 reset_methods[PCI_RESET_METHODS_NUM];
> + struct pci_dev *pdev = to_pci_dev(dev);
> + u8 prio = PCI_RESET_METHODS_NUM;
> + char *name, *options;
> + int i;
Reorder decls with to_pci_dev(dev) first, then in order of use.
> + if (count >= (PAGE_SIZE - 1))
> + return -EINVAL;
> +
> + options = kstrndup(buf, count, GFP_KERNEL);
> + if (!options)
> + return -ENOMEM;
> +
> + /*
> + * Initialize reset_method such that 0xff indicates
> + * supported but not currently enabled reset methods
> + * as we only use priority values which are within
> + * the range of PCI_RESET_FN_METHODS array size
> + */
> + for (i = 0; i < PCI_RESET_METHODS_NUM; i++)
> + reset_methods[i] = pdev->reset_methods[i] ? 0xff : 0;
I'm hoping the 0xff trick goes away with the alternate encoding?
> + if (sysfs_streq(options, "")) {
> + pci_warn(pdev, "All device reset methods disabled by user");
> + goto set_reset_methods;
> + }
I think you can get this case out of the way early with no kstrndup(),
no goto, etc.
> + if (sysfs_streq(options, "default")) {
> + for (i = 0; i < PCI_RESET_METHODS_NUM; i++)
> + reset_methods[i] = reset_methods[i] ? prio-- : 0;
> + goto set_reset_methods;
> + }
If you use pci_init_reset_methods() here, you can also get this case
out of the way early.
> + while ((name = strsep(&options, ",")) != NULL) {
> + if (sysfs_streq(name, ""))
> + continue;
> +
> + name = strim(name);
> +
> + for (i = 0; i < PCI_RESET_METHODS_NUM; i++) {
> + if (reset_methods[i] &&
> + sysfs_streq(name, pci_reset_fn_methods[i].name)) {
> + reset_methods[i] = prio--;
> + break;
> + }
> + }
> +
> + if (i == PCI_RESET_METHODS_NUM) {
> + kfree(options);
> + return -EINVAL;
> + }
> + }
> +
> + if (reset_methods[0] &&
> + reset_methods[0] != PCI_RESET_METHODS_NUM)
> + pci_warn(pdev, "Device specific reset disabled/de-prioritized by user");
Is there a specific reason for this warning? Is it just telling the
user that he might have shot himself in the foot? Not sure that's
necessary.
> +set_reset_methods:
> + kfree(options);
> + memcpy(pdev->reset_methods, reset_methods, sizeof(reset_methods));
> + 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;
I think this _is_visible method is executed only once, at
device_add()-time. That means if a device doesn't support any resets
at that time, "reset_method" will not be visible, and there will be no
way to ever enable a reset method at run-time. I assume that's OK;
just double-checking.
> +
> + 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 +1608,7 @@ 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,
> --
> 2.31.1
>
