From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E438B3D905D for ; Sat, 18 Jul 2026 17:29:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784395744; cv=none; b=ozsiSMLe1kKGqwkqt4HCoSVRmgjhqmQQXvFFGTF3Gvy7MekK3/ReIZEerNGRRI76PabJzCx1oSlGZX3CXh8F3DWLpOse1AV4VW/Ic6h0W/GY97ntfc30JHW1l+Y4jlSfCyRw8nsiBIgmSO/QpTuVCzak0cJgLeJk40oq3nnck/0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784395744; c=relaxed/simple; bh=7K8x2+GBEePl39ZU7AHYccmQWw9KmKGu8EaHrXEobqY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: In-Reply-To:Content-Type:Content-Disposition; b=IHU1s4N35pIHitg3Ict93gKXj0PAvFyNq7ggFmjs9xK8HkKmra10SlU24JsegTsVpIZXfxGtVhTXV2E81aZlWitqo9PXxiwDeX0Qyr7mWENSDvyCdVHOi9p1uYQMJD49Wiwwndqz3ZbDmS6ipzANuBOlgavIOtr0nGFDDvjvn+g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Rddh2ovb; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Rddh2ovb" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784395742; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=FhCQ2Emrbj/HDb8KVno6YlUg/VJvnIV+wiiPmup6hPA=; b=Rddh2ovbZJDD29jH5klP2rOu8TsJpIhnM8vKW5QnY/7U/AQIhGdCru/rU/MgNo9fRN1/hk 9obHCox33fUCUp2BhdOVgTnQaUPTvvZVFjzfqrdITcWCcSXkShHJ8msLhrt6gqKnqfIDQ3 +QgSi3s+SaRO/YYU+KDpDZuRjfRQUlE= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-663-vveZe82BP3eHK0YSl0iV3w-1; Sat, 18 Jul 2026 13:29:00 -0400 X-MC-Unique: vveZe82BP3eHK0YSl0iV3w-1 X-Mimecast-MFC-AGG-ID: vveZe82BP3eHK0YSl0iV3w_1784395739 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-495561cf5dcso673455e9.3 for ; Sat, 18 Jul 2026 10:29:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784395739; x=1785000539; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=FhCQ2Emrbj/HDb8KVno6YlUg/VJvnIV+wiiPmup6hPA=; b=o0wR5oaS1Xj5d2TUrEt59SAz/pYkMasTLp19LgUVXxKxMFczhARJErth7X+o75SaQN jn9NJ7oaFVfWZz/TaR0Jmm5Ow5gjvkR4niqS9PeF072TKekyAk4V6cv2tL3n3NN+eczB Yy+uZz1tY1W3/coS+PCS+xsv/LTMNjGDMc+H4062ETLdP9119+lojor7Z0v/YhuIiwm4 JOceQNkiNf8OKRAB+w+4M2JrPIGuB+TWJc34AKs6B/qxaJKNPqwihuuircWuoEoOozNK hIMAPwWmQuEgGiriHEgapegvavpvgz1iVVrdxKVub0p64JXnZm/I1i8IMLqkPrlCKwwZ j62w== X-Forwarded-Encrypted: i=1; AHgh+Rpc0yNe0CkLP4BgrT7E6r9YrSS1f3YcgoJTROxtJOcH4PfmW73LpCIk8KaUpXCcPMGOkym3VEW8gnbvkYWzdw==@lists.linux.dev X-Gm-Message-State: AOJu0YwpUTDbLK21JiK4f4I/iOqCKOMIp41lZWecwkJaiwQaoZisav+Z pa5QdWDtKOsVxF5hg42fvVAdJ+V7hteATRyzbdCmd3qRW+N2AAHcCkN/FKpNjlEf9hlMneKKpCt IXbzUuEK2H+eBqr+BjZPuvw0avROOEipF3Bwg2kbIt/Ejqo9/3OAFw0skY4HOVCnhGrNg X-Gm-Gg: AfdE7cm7p5Sara64Wcy8fxYT65lCiG2KLDao+77eprZO35oYBfwA5w++C7JU2g7jdwV A3XlEn4gK9zDAIAmzuB03RXp9l9TNuqTkYHDFf8uZxihHxNY+XOkQM8LRigAe8wFcu5a6ZNsROP mE0RLeYmTlxM/0epeUOpmG0BlW2vsKX0+0KfmpEL/9fqGrTHoGfvmtw4mSc+ozgskm+W6Tx/S5p Lf2h2GT3JM0TIJxQPaMb5mq1qFqrdl1ExV8E62dJVHFAtLHbevKfuth06f0CVvqD2XwInO+nPuq JXWdxzmJDV0q3ewM99dxJGBwYHMHenLJgPZIECmV/5FPtyy1A4LeruM6RPOR7T5fx+n5C/h1WJR VXt/AL4pJByO70AABhKKObx2bVrOMM1k= X-Received: by 2002:a05:600c:4512:b0:493:bc4a:fb56 with SMTP id 5b1f17b1804b1-4954a50e92bmr81309895e9.39.1784395739244; Sat, 18 Jul 2026 10:28:59 -0700 (PDT) X-Received: by 2002:a05:600c:4512:b0:493:bc4a:fb56 with SMTP id 5b1f17b1804b1-4954a50e92bmr81309425e9.39.1784395738416; Sat, 18 Jul 2026 10:28:58 -0700 (PDT) Received: from redhat.com (bzq-79-177-145-168.red.bezeqint.net. [79.177.145.168]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49549a47de7sm138584905e9.7.2026.07.18.10.28.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Jul 2026 10:28:57 -0700 (PDT) Date: Sat, 18 Jul 2026 13:28:54 -0400 From: "Michael S. Tsirkin" To: Mauro Carvalho Chehab Cc: Brian Daniels , Mauro Carvalho Chehab , acourbot@google.com, adelva@google.com, aesteve@redhat.com, changyeon@google.com, daniel.almeida@collabora.com, eperezma@redhat.com, gnurou@gmail.com, gurchetansingh@google.com, hverkuil@xs4all.nl, jasowang@redhat.com, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, nicolas.dufresne@collabora.com, virtualization@lists.linux.dev, xuanzhuo@linux.alibaba.com Subject: Re: [PATCH v4 6/8] media: virtio: Add virtio_media_driver Message-ID: <20260718132759-mutt-send-email-mst@kernel.org> References: <20260622171017-mutt-send-email-mst@kernel.org> <20260625201850.2981130-1-briandaniels@google.com> <20260712085726.19198fda@foz.lan> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260712085726.19198fda@foz.lan> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: L5p0TRNtR7u4bXzcGT7VV0c0cprVoNTs5-CQVTGz3qY_1784395739 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sun, Jul 12, 2026 at 08:57:26AM +0200, Mauro Carvalho Chehab wrote: > On Thu, 25 Jun 2026 16:18:48 -0400 > Brian Daniels wrote: > > > > > From: Alexandre Courbot > > > > > > > > virtio_media_driver.c provides the expected driver hooks, and support > > > > for mmapping and polling. > > > > > > > > Signed-off-by: Alexandre Courbot > > > > Co-developed-by: Brian Daniels > > > > Signed-off-by: Brian Daniels > > > > --- > > > > drivers/media/virtio/virtio_media_driver.c | 959 +++++++++++++++++++++ > > > > 1 file changed, 959 insertions(+) > > > > create mode 100644 drivers/media/virtio/virtio_media_driver.c > > > > > > > > diff --git a/drivers/media/virtio/virtio_media_driver.c b/drivers/media/virtio/virtio_media_driver.c > > > > new file mode 100644 > > > > index 000000000..d6363c673 > > > > --- /dev/null > > > > +++ b/drivers/media/virtio/virtio_media_driver.c > > > > @@ -0,0 +1,959 @@ > > > > +// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0+ > > > > + > > > > +/* > > > > + * Virtio-media driver. > > > > + * > > > > + * Copyright (c) 2024-2025 Google LLC. > > > > + */ > > > > + > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > + > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > +#include > > > > + > > > > +#include "protocol.h" > > > > +#include "session.h" > > > > +#include "virtio_media.h" > > > > + > > > > +#define VIRTIO_MEDIA_NUM_EVENT_BUFS 16 > > > > + > > > > +/* ID of the SHM region into which MMAP buffer will be mapped. */ > > > > +#define VIRTIO_MEDIA_SHM_MMAP 0 > > > > + > > > > +/* > > > > + * Name of the driver to expose to user-space. > > > > + * > > > > + * This is configurable because v4l2-compliance has workarounds specific to > > > > + * some drivers. When proxying these directly from the host, this allows it to > > > > + * apply them as needed. > > > > + */ > > > > +char *virtio_media_driver_name; > > > > +module_param_named(driver_name, virtio_media_driver_name, charp, 0660); > > > > > > > > > Um. What? Not how it should be handled. > > > > I can remove this module param. I didn't end up using this when compliance testing. > > Instead, I patched v4l-utils: > > https://lore.kernel.org/all/20260528163448.4031965-1-briandaniels@google.com/ > > > > Let me know if you think the v4l-utils patch is a good approach, otherwise let > > me know how you'd prefer to address the v4l2-compliance driver-specific workounds > > when they're being proxied with virtio-media. > > This kind of discussion should happen on a separate PR for v4l2-compliance, > c/c to the proper developers and maintainers of it. I wonder how migration can work when guest is tied to host driver model like this. > > > > > > + > > > > +/* > > > > + * Whether USERPTR buffers are allowed. > > > > + * > > > > + * This is disabled by default as USERPTR buffers are dangerous, but the option > > > > + * is left to enable them if desired. > > > > + */ > > > > +bool virtio_media_allow_userptr; > > > > +module_param_named(allow_userptr, virtio_media_allow_userptr, bool, 0660); > > > > > > > > > is this kind of thing common? > > There is one old media device that has it (saa7134). > > > > > To be honest, I don't really know. I'm also not that familiar with the USERPTR > > issues. I see a few references online about their use being discouraged due to > > possible race conditions, perhaps that was the original motivation for this > > parameter (I'm not the original author of this driver). > > > > I'm open to alternatives, feel free to let me know if you have a preference. > > We tend to not implement USERPTR on newer drivers. I suggest you > to place the logic with regards to V4L2_MEMORY_USERPTR on a separate > patch for further discussions. > > > > > > > + > > > > +/** > > > > + * virtio_media_session_alloc - Allocate a new session. > > > > + * @vv: virtio-media device the session belongs to. > > > > + * @id: ID of the session. > > > > + * @nonblocking_dequeue: whether dequeuing of buffers should be blocking or > > > > + * not. > > > > + * > > > > + * The ``id`` and ``list`` fields must still be set by the caller. > > > > > > still in what sense? > > > > Based on the code below, I'm not so sure that the caller is responsible for > > setting these values. They seem to be initialized in the function. > > > > Perhaps Alexandre Courbot (the original author) would know more. Unless he > > says otherwise though I'm inclined to remove this comment. > > > > > > + */ > > > > +static struct virtio_media_session * > > > > +virtio_media_session_alloc(struct virtio_media *vv, u32 id, > > > > + struct file *file) > > > > +{ > > > > + struct virtio_media_session *session; > > > > + int i; > > > > + int ret; > > > > + > > > > + session = kzalloc_obj(*session, GFP_KERNEL); > > > > + if (!session) > > > > + goto err_session; > > > > + > > > > + session->shadow_buf = kzalloc(VIRTIO_SHADOW_BUF_SIZE, GFP_KERNEL); > > > > + if (!session->shadow_buf) > > > > + goto err_shadow_buf; > > > > + > > > > + ret = sg_alloc_table(&session->command_sgs, DESC_CHAIN_MAX_LEN, > > > > + GFP_KERNEL); > > > > + if (ret) > > > > + goto err_payload_sgs; > > > > + > > > > + session->id = id; > > > > + session->nonblocking_dequeue = file->f_flags & O_NONBLOCK; > > > > + > > > > + INIT_LIST_HEAD(&session->list); > > > > + v4l2_fh_init(&session->fh, &vv->video_dev); > > > > + virtio_media_session_fh_add(session, file); > > > > + > > > > + for (i = 0; i <= VIRTIO_MEDIA_LAST_QUEUE; i++) > > > > + INIT_LIST_HEAD(&session->queues[i].pending_dqbufs); > > > > + mutex_init(&session->queues_lock); > > > > + > > > > + init_waitqueue_head(&session->dqbuf_wait); > > > > + > > > > + mutex_lock(&vv->sessions_lock); > > > > + list_add_tail(&session->list, &vv->sessions); > > > > + mutex_unlock(&vv->sessions_lock); > > > > + > > > > + return session; > > > > + > > > > +err_payload_sgs: > > > > + kfree(session->shadow_buf); > > > > +err_shadow_buf: > > > > + kfree(session); > > > > +err_session: > > > > + return ERR_PTR(-ENOMEM); > > > > +} > > > > + > > > > +/** > > > > + * virtio_media_session_free - Free all resources of a session. > > > > + * @vv: virtio-media device the session belongs to. > > > > + * @session: session to destroy. > > > > + * > > > > + * All the resources of @sesssion, as well as the backing memory of @session > > > > + * itself, are freed. > > > > > > why @ here and `` above? And typo in the name. > > > > The `@` here was an attempt to follow the guide here for referencing function > > parameters: > > https://docs.kernel.org/doc-guide/kernel-doc.html#highlights-and-cross-references > > Yes. This is part of Linux Kernel kernel-doc markup: when referring to > struct fields, you should use @field (or ``field`` if one wants to place an > asterisk on it, like ``*field``). > > > > > That being said, I don't believe this file is 100% consistent with that. I will > > spend some time cleaning up the comments throughout this patch set to get them > > consistent for v5. Thanks! > > Please use it on a consistent way along the driver. > > > Thanks, > Mauro