Hi Michael,
On 06/25/2013 07:51 PM, Michael Banken wrote:
> This check greatly simplifies creating a dummy hid device.
Could you elaborate a little here? If you want to create a hid device
from the user space, I encourage you to use uhid, which is available
since v3.6.
> With this check in place a hid dummy can be created simply by allocating and adding the device.
> This used to be possible in earlier Kernel versions.
>
> Signed-off-by: Michael Banken <michael.banken@xxxxxxxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Lorenz Haspel <lorenz@xxxxxxxxxxx>
> ---
> drivers/hid/hid-core.c | 37 ++++++++++++++++++++-----------------
> 1 file changed, 20 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 0951a9a..88c573e 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -2289,24 +2289,27 @@ int hid_add_device(struct hid_device *hdev)
> if (hid_ignore(hdev))
> return -ENODEV;
>
> - /*
> - * Read the device report descriptor once and use as template
> - * for the driver-specific modifications.
> - */
> - ret = hdev->ll_driver->parse(hdev);
> - if (ret)
> - return ret;
> - if (!hdev->dev_rdesc)
> - return -ENODEV;
> -
> - /*
> - * Scan generic devices for group information
> - */
> - if (hid_ignore_special_drivers ||
> - !hid_match_id(hdev, hid_have_special_driver)) {
> - ret = hid_scan_report(hdev);
> + if (hdev->ll_driver != NULL) {
I am concerned by the fact that *every* hid specific driver will have to
call hid_hw_start and hid_hw_stop at some point. These 2 functions are
not protected against a null pointer in hdev->ll_driver, so allowing
here a null pointer will introduce a kernel oops later.
I think it would be safer to have:
if (!hdev->ll_driver)
return -ENODEV;
But if I understood correctly, this is not your point.
So definitively, I need your usage scenarios of such hid "dummy" device.
Cheers,
Benjamin
> + /*
> + * Read the device report descriptor once and use as template
> + * for the driver-specific modifications.
> + */
> + ret = hdev->ll_driver->parse(hdev);
> if (ret)
> - hid_warn(hdev, "bad device descriptor (%d)\n", ret);
> + return ret;
> + if (!hdev->dev_rdesc)
> + return -ENODEV;
> +
> + /*
> + * Scan generic devices for group information
> + */
> + if (hid_ignore_special_drivers ||
> + !hid_match_id(hdev, hid_have_special_driver)) {
> + ret = hid_scan_report(hdev);
> + if (ret)
> + hid_warn(hdev,
> + "bad device descriptor (%d)\n", ret);
> + }
> }
>
> /* XXX hack, any other cleaner solution after the driver core
>
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