Date:	Tue, 20 Jan 2015 09:09:37 -0500
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Jim Keir <jimkeir@...cledbadirect.com>
Cc:	linux-input <linux-input@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	Jiri Kosina <jkosina@...e.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 001/001] usbhid: Fix initialisation and force effect
 modifications for the Microsoft Sidewinder Force Feedback Pro 2 joystick

Hi,

Jim, in addition to what Alan said, here are some comments that I
would like to be fixed in the v2.

On Sun, Jan 18, 2015 at 11:07 AM, Jim Keir <jimkeir@...cledbadirect.com> wrote:
> From: Jim Keir <jimkeir@...oo.co.uk>
> Signed-off-by: Jim Keir <jimkeir@...oo.co.uk>
>

The Signed-off-by line is generally at the end of the commit message.
This way, if someone else adds new changes to the patch, we can trace
which modifications belongs to which.

> Currently the SWFF2 driver fails during initialisation, making the force
> capability of the joystick unusable. Further, there is a long-standing
> bug in the same driver where commands to update force parameters are
> addressed to the last-created force effect instead of the specified one,
> making it impossible to modify effects after their creation.
>
> Three bugs are addressed:
>
> 1) The FF2 driver (usbhid/hid-pidff.c) sends commands to the stick
> during ff_init. However, this is called inside a block where
> driver_input_lock is locked, so the results of these initial commands
> are discarded. This one is the "killer", without this nothing else works.
>
> ff_init issues commands using "hid_hw_request". This eventually goes to
> hid_input_report, which returns -EBUSY because driver_input_lock is
> locked. The change is to delay the ff_init call in hid-core.c until
> after this lock has been released.
>
> 2) The usbhid driver ignores an endpoint stall when sending control
> commands, causing the first few commands of the hid-pidff.c
> initialisation to get lost.
>
> usbhid/hid-core.c has been modified by copying lines into "hid_ctrl"
> from the "hid_irq_in" function in the same file.
>
> 3) The FF2 driver (usbhid/hid-pidff.c) does not set the effect ID when
> uploading an effect. The result is that the initial upload works but
> subsequent uploads to modify effect parameters are all directed at the
> last-created effect.
>

Fully agree that you should split the commit in 3 if there are 3
issues (and to the rest Alan said also, but this is the most important
I think).


> The targeted effect ID must be passed back to the device when effect
> parameters are changed. This is done at the start of
> "pidff_set_condition_report", "pidff_set_periodic_report" etc. based on
> the value of "pidff->block_load[PID_EFFECT_BLOCK_INDEX].value[0]".
> However, this value is only ever set during pidff_request_effect_upload.
> The result is stored in "pidff->pid_id[effect->id]" at the end of
> pid_upload_effect, for later use. However, if an effect is modified and
> re-sent then this identifier is not being copied back from
> pidff->pid_id[effect->id] before sending the command to the device. The
> fix is to do this at the start of pidff_upload_effect.
>
> This patch taken against kernel 3.13.0
>
> ---
>
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 905e40a..a608ee6 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -1546,9 +1546,8 @@ int hid_connect(struct hid_device *hdev, unsigned int
> connect_mask)

On my local tree, hid_connect is at 1562. Is your patch based on the
for-next branch of the HID tree?
https://git.kernel.org/cgit/linux/kernel/git/jikos/hid.git


>          return -ENODEV;
>      }
>
> -    if ((hdev->claimed & HID_CLAIMED_INPUT) &&
> -            (connect_mask & HID_CONNECT_FF) && hdev->ff_init)
> -        hdev->ff_init(hdev);
> +    /* Removed ff_init() call from here. It does device I/O but this
> +     * is blocked because driver_input_lock is currently locked. */

Please don't. If the feedback driver needs to have access to the IO
earlier, it needs to call hid_device_io_start() (and eventually
hid_device_io_stop() if some other initialization are required).

>
>      len = 0;
>      if (hdev->claimed & HID_CLAIMED_INPUT)
> @@ -2029,6 +2028,13 @@ static int hid_device_probe(struct device *dev)
>  unlock:
>      if (!hdev->io_started)
>          up(&hdev->driver_input_lock);
> +
> +    if ((hdev->claimed & HID_CLAIMED_INPUT) && hdev->ff_init) {
> +        /* Late init of PID force-feedback drivers moved to after
> +         * unlock of driver_input_lock */
> +        hdev->ff_init(hdev);
> +    }
> +

Same comment as above.

>  unlock_driver_lock:
>      up(&hdev->driver_lock);
>      return ret;
> diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
> index 029965e..5d34dd7 100644
> --- a/drivers/hid/usbhid/hid-core.c
> +++ b/drivers/hid/usbhid/hid-core.c
> @@ -505,7 +505,12 @@ static void hid_ctrl(struct urb *urb)
>      case -EPROTO:        /* protocol error or unplug */
>      case -ECONNRESET:    /* unlink */
>      case -ENOENT:
> +        break;
>      case -EPIPE:        /* report not available */
> +        usbhid_mark_busy(usbhid);
> +        clear_bit(HID_IN_RUNNING, &usbhid->iofl);
> +        set_bit(HID_CLEAR_HALT, &usbhid->iofl);
> +        schedule_work(&usbhid->reset_work);
>          break;
>      default:        /* error */
>          hid_warn(urb->dev, "ctrl urb status %d received\n", status);
> diff --git a/drivers/hid/usbhid/hid-pidff.c b/drivers/hid/usbhid/hid-pidff.c
> index 10b6167..3f8ea63 100644
> --- a/drivers/hid/usbhid/hid-pidff.c
> +++ b/drivers/hid/usbhid/hid-pidff.c
> @@ -568,6 +568,13 @@ static int pidff_upload_effect(struct input_dev *dev,
> struct ff_effect *effect,
>      int type_id;
>      int error;
>
> +    pidff->block_load[PID_EFFECT_BLOCK_INDEX].value[0] = 0;
> +
> +    if (old && effect) {
> +        pidff->block_load[PID_EFFECT_BLOCK_INDEX].value[0] =
> +            pidff->pid_id[effect->id];
> +    }
> +
>      switch (effect->type) {
>      case FF_CONSTANT:
>          if (!old) {
> @@ -701,10 +708,14 @@ static int pidff_upload_effect(struct input_dev *dev,
> struct ff_effect *effect,
>          return -EINVAL;
>      }
>
> -    if (!old)
> +    if (!old) {
>          pidff->pid_id[effect->id] =
>              pidff->block_load[PID_EFFECT_BLOCK_INDEX].value[0];
>
> +        hid_dbg(pidff->hid, "Created new effect of type 0x%02x with h/w ID
> %d, driver ID %d\n",
> +            effect->type, pidff->pid_id[effect->id], effect->id);
> +    }
> +

Not sure this is absolutely required, but it shouldn't hurt so you can
keep it I guess.

Cheers,
Benjamin

>      hid_dbg(pidff->hid, "uploaded\n");
>
>      return 0;
>
>
>
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