linux-kernel - Re: [PATCH 1/1] media: dvbsky: use a single mutex and state buffers for all R/W ops

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Date:   Sun, 29 Sep 2019 23:40:16 +0200
From:   JP <jp@...w.nl>
To:     Andrei Koshkosh <andreykosh000@...l.ru>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, Sean Young <sean@...s.org>,
        Stefan Brüns <stefan.bruens@...h-aachen.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] media: dvbsky: use a single mutex and state buffers
 for all R/W ops

This works very well for me.
(and please see unrelated comment below)

On 9/29/19 10:04 AM, Andrei Koshkosh wrote:
> Signed-off-by: Andrei Koshkosh <andreykosh000@...l.ru>
> ---
>   drivers/media/usb/dvb-usb-v2/dvbsky.c | 16 ++++++++--------
>   1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/usb/dvb-usb-v2/dvbsky.c b/drivers/media/usb/dvb-usb-v2/dvbsky.c
> index c41e10b..6a118a0 100644
> --- a/drivers/media/usb/dvb-usb-v2/dvbsky.c
> +++ b/drivers/media/usb/dvb-usb-v2/dvbsky.c
> @@ -22,7 +22,6 @@ MODULE_PARM_DESC(disable_rc, "Disable inbuilt IR receiver.");
>   DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
>   
>   struct dvbsky_state {
> -	struct mutex stream_mutex;
>   	u8 ibuf[DVBSKY_BUF_LEN];
>   	u8 obuf[DVBSKY_BUF_LEN];
>   	u8 last_lock;
> @@ -61,16 +60,18 @@ static int dvbsky_stream_ctrl(struct dvb_usb_device *d, u8 onoff)
>   {
>   	struct dvbsky_state *state = d_to_priv(d);
>   	int ret;
> -	u8 obuf_pre[3] = { 0x37, 0, 0 };
> -	u8 obuf_post[3] = { 0x36, 3, 0 };
> +	static u8 obuf_pre[3] = { 0x37, 0, 0 };
> +	static u8 obuf_post[3] = { 0x36, 3, 0 };
>   
> -	mutex_lock(&state->stream_mutex);
> -	ret = dvbsky_usb_generic_rw(d, obuf_pre, 3, NULL, 0);
> +	mutex_lock(&d->usb_mutex);
> +	memcpy(state->obuf, obuf_pre, 3);
> +	ret = dvb_usbv2_generic_write_locked(d, state->obuf, 3);
>   	if (!ret && onoff) {
>   		msleep(20);
> -		ret = dvbsky_usb_generic_rw(d, obuf_post, 3, NULL, 0);
> +		memcpy(state->obuf, obuf_post, 3);
> +		ret = dvb_usbv2_generic_write_locked(d, state->obuf, 3);
>   	}
> -	mutex_unlock(&state->stream_mutex);
> +	mutex_unlock(&d->usb_mutex);
>   	return ret;
>   }
>   
> @@ -599,7 +600,6 @@ static int dvbsky_init(struct dvb_usb_device *d)
>   	if (ret)
>   		return ret;
>   	*/
commented-out code has call to non-existing function.

> -	mutex_init(&state->stream_mutex);
>   
>   	state->last_lock = 0;
>   
Thanks,
Jan Pieter.