linux-kernel - Re: [PATCH] HID: surface-hid: Fix get-report request

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Message-ID: <nycvar.YFH.7.76.2106151055080.18969@cbobk.fhfr.pm>
Date:   Tue, 15 Jun 2021 10:55:20 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Maximilian Luz <luzmaximilian@...il.com>
cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Blaž Hrastnik <blaz@...n.io>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: surface-hid: Fix get-report request

On Tue, 8 Jun 2021, Maximilian Luz wrote:

> Getting a report (e.g. feature report) from a device requires us to send
> a request indicating which report we want to retrieve and then waiting
> for the corresponding response containing that report. We already
> provide the response structure to the request call, but the request
> isn't marked as a request that expects a response. Thus the request
> returns before we receive the response and the response buffer indicates
> a zero length response due to that.
> 
> This essentially means that the get-report calls are broken and will
> always indicate that a report of length zero has been read.
> 
> Fix this by appropriately marking the request.
> 
> Fixes: b05ff1002a5c ("HID: Add support for Surface Aggregator Module HID transport")
> Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>
> ---
>  drivers/hid/surface-hid/surface_hid.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hid/surface-hid/surface_hid.c b/drivers/hid/surface-hid/surface_hid.c
> index 3477b31611ae..a3a70e4f3f6c 100644
> --- a/drivers/hid/surface-hid/surface_hid.c
> +++ b/drivers/hid/surface-hid/surface_hid.c
> @@ -143,7 +143,7 @@ static int ssam_hid_get_raw_report(struct surface_hid_device *shid, u8 rprt_id,
>  	rqst.target_id = shid->uid.target;
>  	rqst.instance_id = shid->uid.instance;
>  	rqst.command_id = SURFACE_HID_CID_GET_FEATURE_REPORT;
> -	rqst.flags = 0;
> +	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
>  	rqst.length = sizeof(rprt_id);
>  	rqst.payload = &rprt_id;

Queued in for-5.13/upstream-fixes branch, thanks.

-- 
Jiri Kosina
SUSE Labs