From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40AC6C433EF for ; Mon, 27 Sep 2021 10:49:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 23B8360F4B for ; Mon, 27 Sep 2021 10:49:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233890AbhI0KvE (ORCPT ); Mon, 27 Sep 2021 06:51:04 -0400 Received: from perceval.ideasonboard.com ([213.167.242.64]:38494 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233895AbhI0KvC (ORCPT ); Mon, 27 Sep 2021 06:51:02 -0400 Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 4E29CB91; Mon, 27 Sep 2021 12:49:23 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1632739763; bh=whbc43g3sJlMalY+vbgUfYGRhTWhydTGPHqhqJaEank=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PcX3fRM9B0uJ3PVcy/rpajHlU4gSI6eHyFuwGlhGePmsqz0kM/x8gBouVvR3LEkrR ekfdPdIacNtKbmE4fnc7tDTNblartFVq6oreqTPUrNd5SfRgXywbdNirbsTjzuTSg2 xqf/kTdpe5RTrVapJOB9Wv0is7WJXNRKlUCRJDzA= Date: Mon, 27 Sep 2021 13:49:17 +0300 From: Laurent Pinchart To: Tomi Valkeinen Cc: Jacopo Mondi , linux-media@vger.kernel.org, sakari.ailus@linux.intel.com, Jacopo Mondi , niklas.soderlund+renesas@ragnatech.se, Mauro Carvalho Chehab , Hans Verkuil , Pratyush Yadav , Lokesh Vutla Subject: Re: [PATCH v8 03/36] media: subdev: add 'which' to subdev state Message-ID: References: <20210830110116.488338-1-tomi.valkeinen@ideasonboard.com> <20210830110116.488338-4-tomi.valkeinen@ideasonboard.com> <20210913114154.ovffxjoghgdud4js@uno.localdomain> <0733ae28-bcd9-6dc8-fb6a-0fa43beb1191@ideasonboard.com> <20210913133841.nck65h2ft4hfnbg5@uno.localdomain> <656577a3-b783-0272-4809-20169b84e891@ideasonboard.com> <20210916130752.bsdhq3xpsatdfl4a@uno.localdomain> <9d80e73b-acd0-9439-8447-6c2a66686ec3@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <9d80e73b-acd0-9439-8447-6c2a66686ec3@ideasonboard.com> Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi Tomi, On Mon, Sep 27, 2021 at 11:55:38AM +0300, Tomi Valkeinen wrote: > On 27/09/2021 03:48, Laurent Pinchart wrote: > > On Thu, Sep 16, 2021 at 04:24:19PM +0300, Tomi Valkeinen wrote: > >> On 16/09/2021 16:07, Jacopo Mondi wrote: > >> > >>> Also note that operations like s_stream do not take a state as > >>> parameter. The driver has to fetch it from the subdev anyway > >>> (this in reply to the idea of having the active state as parameter vs > >>> retrieving it from the subdev if ACTIVE) > >>> > >>> While porting the R-Car drivers on top of this series I found myself > >>> in the need to (in the s_stream call chain) > >>> > >>> static int rcsi2_start_receiver(struct rcar_csi2 *priv) > >>> { > >>> const struct v4l2_subdev_state *state = priv->subdev.state; > >>> const struct v4l2_subdev_stream_configs *configs = &state->stream_configs; > >>> > >>> ... > >>> > >>> /* > >>> * Configure field handling inspecting the formats of the > >>> * single sink pad streams. > >>> */ > >>> for (i = 0; i < configs->num_configs; ++i) { > >>> const struct v4l2_subdev_stream_config *config = configs->configs; > >>> if (config->pad != RCAR_CSI2_SINK) > >>> continue; > >>> > >>> if (config->fmt.field != V4L2_FIELD_ALTERNATE) > >>> continue; > >>> > >>> fld |= FLD_DET_SEL(1); > >>> fld |= FLD_FLD_EN(config->stream); > >>> > >>> /* PAL vs NTSC. */ > >>> if (config->fmt.height == 240) > >>> fld |= FLD_FLD_NUM(0); > >>> else > >>> fld |= FLD_FLD_NUM(1); > >>> } > >>> > >>> ... > >>> > >>> } > >>> > >>> Am I doing it wrong, or is this a case for the subdev to have to > >>> directly access sd->state ? > >> > >> In s_stream path you should: > >> > >> state = v4l2_subdev_lock_active_state(sd); > >> > >> > >> > >> v4l2_subdev_unlock_state(state); > >> > >> If you already have the state, e.g. in set_fmt: > >> > >> state = v4l2_subdev_validate_and_lock_state(sd, state); > >> > >> > >> > >> v4l2_subdev_unlock_state(state); > >> > >> Accessing the stream_configs directly is fine but not that nice. I did > >> think about some helpers, perhaps for_each_stream_config(), but I didn't > >> add that as I didn't have the need. > >> > >> There's v4l2_state_get_stream_format() which can be used in many cases, > >> but we probably need something else if you need to iterate over all the > >> configs. > > > > I really like forcing drivers to call functions that will lock the > > state, at least until we can move the locks to the core (if ever). We > > should move the fields of v4l2_subdev that drivers are not supposed to > > access directly under a big PRIVATE comment. > > Can you clarify what you mean here? Did you mean you like functions that > will _check_ the lock? Or did you just mean that you like > v4l2_subdev_lock_state() better than mutex_lock(state->lock)? I like v4l2_subdev_lock_state(). > Well, in any case, I think my series does both =). I can add the private > comment to subdev. In fact, at one time I did not have sd->state, but > sd->_state, just to make sure no one accesses it. I half recall there was a gcc attribute to mark private fields in a structure, which then generates a warning if those fields are accessed by a function that doesn't have another special attribute. Or maybe I was dreaming :-) -- Regards, Laurent Pinchart