Re: [Linux-kernel-mentees] [PATCH v2 1/3] PCI: sysfs: Define device attributes with DEVICE_ATTR*()

Kelsey Skunberg
2019-08-15T15:54:33Z

On Wed, Aug 14, 2019 at 09:52:20AM +0200, Greg KH wrote:
> On Tue, Aug 13, 2019 at 02:45:11PM -0600, Kelsey Skunberg wrote:
> > Defining device attributes should be done through the helper
> > DEVICE_ATTR*(_name, _mode, _show, _store). Change all instances using
> > __ATTR*() to now use DEVICE_ATTR*().
> >
> > Example of old:
> >
> > struct device_attribute dev_attr_##_name = __ATTR(_name, _mode, _show,
> > _store)
> >
> > Example of new:
> >
> > static DEVICE_ATTR(foo, S_IWUSR | S_IRUGO, show_foo, store_foo)
>
> Why not DEVICE_ATTR_RO() and DEVICE_ATTR_RW() and friends? "Raw"
> DEVICE_ATTR() should almost never be used unless the files have a very
> strange mode setting. And if that is true, they should be audited to
> find out why their permissions are so strange from the rest of the
> kernel defaults.
>

I updated the commit log to show a more encouraged example and a couple
of the DEVICE_ATTR() into DEVICE_ATTR_WO() in a new patch while adding
that patch to the series.

> >
> > Signed-off-by: Kelsey Skunberg <skunberg.kelsey@gmail.com>
> > ---
> > drivers/pci/pci-sysfs.c | 59 +++++++++++++++++++----------------------
> > 1 file changed, 27 insertions(+), 32 deletions(-)
> >
> > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > index 965c72104150..8af7944fdccb 100644
> > --- a/drivers/pci/pci-sysfs.c
> > +++ b/drivers/pci/pci-sysfs.c
> > @@ -464,9 +464,7 @@ static ssize_t dev_rescan_store(struct device *dev,
> > }
> > return count;
> > }
> > -static struct device_attribute dev_rescan_attr = __ATTR(rescan,
> > - (S_IWUSR|S_IWGRP),
> > - NULL, dev_rescan_store);
> > +static DEVICE_ATTR(rescan, (S_IWUSR | S_IWGRP), NULL, dev_rescan_store);
>
> DEVICE_ATTR_WO()?
>

This was changed.

> > static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
> > const char *buf, size_t count)
> > @@ -480,9 +478,8 @@ static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
> > pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
> > return count;
> > }
> > -static struct device_attribute dev_remove_attr = __ATTR_IGNORE_LOCKDEP(remove,
> > - (S_IWUSR|S_IWGRP),
> > - NULL, remove_store);
> > +static DEVICE_ATTR_IGNORE_LOCKDEP(remove, (S_IWUSR | S_IWGRP), NULL,
> > + remove_store);
>
> DEVICE_ATTR_WO()?
>
> Ugh, no lockdep? ick, ok, leave this as-is, crazy "remove" files...
>
> >
> > static ssize_t dev_bus_rescan_store(struct device *dev,
> > struct device_attribute *attr,
> > @@ -504,7 +501,7 @@ static ssize_t dev_bus_rescan_store(struct device *dev,
> > }
> > return count;
> > }
> > -static DEVICE_ATTR(rescan, (S_IWUSR|S_IWGRP), NULL, dev_bus_rescan_store);
> > +static DEVICE_ATTR(bus_rescan, (S_IWUSR | S_IWGRP), NULL, dev_bus_rescan_store);
>
> DEVICE_ATTR_WO()?
>

As well as this one.

> >
> > #if defined(CONFIG_PM) && defined(CONFIG_ACPI)
> > static ssize_t d3cold_allowed_store(struct device *dev,
> > @@ -687,16 +684,14 @@ static ssize_t sriov_drivers_autoprobe_store(struct device *dev,
> > return count;
> > }
> >
> > -static struct device_attribute sriov_totalvfs_attr = __ATTR_RO(sriov_totalvfs);
> > -static struct device_attribute sriov_numvfs_attr =
> > - __ATTR(sriov_numvfs, (S_IRUGO|S_IWUSR|S_IWGRP),
> > - sriov_numvfs_show, sriov_numvfs_store);
> > -static struct device_attribute sriov_offset_attr = __ATTR_RO(sriov_offset);
> > -static struct device_attribute sriov_stride_attr = __ATTR_RO(sriov_stride);
> > -static struct device_attribute sriov_vf_device_attr = __ATTR_RO(sriov_vf_device);
> > -static struct device_attribute sriov_drivers_autoprobe_attr =
> > - __ATTR(sriov_drivers_autoprobe, (S_IRUGO|S_IWUSR|S_IWGRP),
> > - sriov_drivers_autoprobe_show, sriov_drivers_autoprobe_store);
> > +static DEVICE_ATTR_RO(sriov_totalvfs);
> > +static DEVICE_ATTR(sriov_numvfs, (S_IRUGO | S_IWUSR | S_IWGRP),
> > + sriov_numvfs_show, sriov_numvfs_store);
>
> DEVICE_ATTR_RW()?
>
> > +static DEVICE_ATTR_RO(sriov_offset);
> > +static DEVICE_ATTR_RO(sriov_stride);
> > +static DEVICE_ATTR_RO(sriov_vf_device);
> > +static DEVICE_ATTR(sriov_drivers_autoprobe, (S_IRUGO | S_IWUSR | S_IWGRP),
> > + sriov_drivers_autoprobe_show, sriov_drivers_autoprobe_store);
>
> DEVICE_ATTR_RW()?
>

Since the DEVICE_ATTR_RW() would change the permissions to '0644', I left
these alone for now. Once confirmed which direction to go, it is my
intention to either add a comment stating the permission '0664' is okay to
use here, or changing the permissions accordingly. This will be
accomplished in a separate patch.

> > #endif /* CONFIG_PCI_IOV */
> >
> > static ssize_t driver_override_store(struct device *dev,
> > @@ -792,7 +787,7 @@ static struct attribute *pcie_dev_attrs[] = {
> > };
> >
> > static struct attribute *pcibus_attrs[] = {
> > - &dev_attr_rescan.attr,
> > + &dev_attr_bus_rescan.attr,
> > &dev_attr_cpuaffinity.attr,
> > &dev_attr_cpulistaffinity.attr,
> > NULL,
> > @@ -820,7 +815,7 @@ static ssize_t boot_vga_show(struct device *dev, struct device_attribute *attr,
> > !!(pdev->resource[PCI_ROM_RESOURCE].flags &
> > IORESOURCE_ROM_SHADOW));
> > }
> > -static struct device_attribute vga_attr = __ATTR_RO(boot_vga);
> > +static DEVICE_ATTR_RO(boot_vga);
> >
> > static ssize_t pci_read_config(struct file *filp, struct kobject *kobj,
> > struct bin_attribute *bin_attr, char *buf,
> > @@ -1458,7 +1453,7 @@ static ssize_t reset_store(struct device *dev, struct device_attribute *attr,
> > return count;
> > }
> >
> > -static struct device_attribute reset_attr = __ATTR(reset, 0200, NULL, reset_store);
> > +static DEVICE_ATTR(reset, 0200, NULL, reset_store);
>
> DEVICE_ATTR_WO()? Hm, root only, maybe not :(
>
> >
> > static int pci_create_capabilities_sysfs(struct pci_dev *dev)
> > {
> > @@ -1468,7 +1463,7 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev)
> > pcie_aspm_create_sysfs_dev_files(dev);
> >
> > if (dev->reset_fn) {
> > - retval = device_create_file(&dev->dev, &reset_attr);
> > + retval = device_create_file(&dev->dev, &dev_attr_reset);
>
> odds are this needs to be fixed up later to use attribute groups
> properly. But that's better left for another patch.
>
> > if (retval)
> > goto error;
> > }
> > @@ -1553,7 +1548,7 @@ static void pci_remove_capabilities_sysfs(struct pci_dev *dev)
> > pcie_vpd_remove_sysfs_dev_files(dev);
> > pcie_aspm_remove_sysfs_dev_files(dev);
> > if (dev->reset_fn) {
> > - device_remove_file(&dev->dev, &reset_attr);
> > + device_remove_file(&dev->dev, &dev_attr_reset);
>
> Same here, attribute groups will handle this.
>
> thanks,
>
> greg k-h

Thank you for pointing these others out, too. I appreciate all your help
with this, Greg. Let me know if there's anything else you spot you'd like
changed.

-Kelsey