On Tue, 04 Feb 2020 16:05:43 -0700
Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
> Allow bus drivers to provide their own callback to match a device to
> the user provided string.
>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
> drivers/vfio/vfio.c | 19 +++++++++++++++----
> include/linux/vfio.h | 3 +++
> 2 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 388597930b64..dda1726adda8 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -875,11 +875,22 @@ EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
> static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,
> char *buf)
> {
> - struct vfio_device *it, *device = NULL;
> + struct vfio_device *it, *device = ERR_PTR(-ENODEV);
>
> mutex_lock(&group->device_lock);
> list_for_each_entry(it, &group->device_list, group_next) {
> - if (!strcmp(dev_name(it->dev), buf)) {
> + int ret;
> +
> + if (it->ops->match) {
> + ret = it->ops->match(it->device_data, buf);
> + if (ret < 0 && ret != -ENODEV) {
> + device = ERR_PTR(ret);
> + break;
> + }
> + } else
> + ret = strcmp(dev_name(it->dev), buf);
The asymmetric braces look a bit odd.
> +
> + if (!ret) {
> device = it;
> vfio_device_get(device);
> break;
> @@ -1441,8 +1452,8 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
> return -EPERM;
>
> device = vfio_device_get_from_name(group, buf);
> - if (!device)
> - return -ENODEV;
> + if (IS_ERR(device))
> + return PTR_ERR(device);
>
> ret = device->ops->open(device->device_data);
> if (ret) {
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index e42a711a2800..755e0f0e2900 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -26,6 +26,8 @@
> * operations documented below
> * @mmap: Perform mmap(2) on a region of the device file descriptor
> * @request: Request for the bus driver to release the device
> + * @match: Optional device name match callback (return: 0 for match, -ENODEV
> + * (or >0) for no match and continue, other -errno: no match and stop)
I'm wondering about these conventions.
If you basically want a tri-state return (match, don't match/continue,
don't match/stop), putting -ENODEV and >0 together feels odd. I would
rather expect either
- < 0 == don't match/stop, 0 == don't match/continue, > 0 == match, or
- 0 == match, -ENODEV (or some other defined error) == don't
match/continue, all other values == don't match/abort?
> */
> struct vfio_device_ops {
> char *name;
> @@ -39,6 +41,7 @@ struct vfio_device_ops {
> unsigned long arg);
> int (*mmap)(void *device_data, struct vm_area_struct *vma);
> void (*request)(void *device_data, unsigned int count);
> + int (*match)(void *device_data, char *buf);
> };
>
> extern struct iommu_group *vfio_iommu_group_get(struct device *dev);
>
