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Tue, 28 Apr 2026 21:31:38 +0200 (CEST) Message-ID: <1b5b03df1f059f10cc990dcc23280cba429e2b60.camel@collabora.com> Subject: Re: [PATCH 03/11] media: Add tgid and fd fields in v4l2_fh struct From: Nicolas Dufresne To: Detlev Casanova , linux-kernel@vger.kernel.org Cc: Benjamin Gaignard , Philipp Zabel , Mauro Carvalho Chehab , Heiko Stuebner , Daniel Almeida , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Hans Verkuil , Laurent Pinchart , Ricardo Ribalda , Yunke Cao , Sakari Ailus , Pavan Bobba , James Cowgill , Ma Ke , Jacopo Mondi , Daniel Scally , linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-trace-kernel@vger.kernel.org, kernel@collabora.com Date: Tue, 28 Apr 2026 15:31:37 -0400 In-Reply-To: <20260212162328.192217-4-detlev.casanova@collabora.com> References: <20260212162328.192217-1-detlev.casanova@collabora.com> <20260212162328.192217-4-detlev.casanova@collabora.com> Autocrypt: addr=nicolas.dufresne@collabora.com; prefer-encrypt=mutual; keydata=mDMEaCN2ixYJKwYBBAHaRw8BAQdAM0EHepTful3JOIzcPv6ekHOenE1u0vDG1gdHFrChD /e0J05pY29sYXMgRHVmcmVzbmUgPG5pY29sYXNAbmR1ZnJlc25lLmNhPoicBBMWCgBEAhsDBQsJCA cCAiICBhUKCQgLAgQWAgMBAh4HAheABQkJZfd1FiEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrjo CGQEACgkQ2UGUUSlgcvQlQwD/RjpU1SZYcKG6pnfnQ8ivgtTkGDRUJ8gP3fK7+XUjRNIA/iXfhXMN abIWxO2oCXKf3TdD7aQ4070KO6zSxIcxgNQFtDFOaWNvbGFzIER1ZnJlc25lIDxuaWNvbGFzLmR1Z nJlc25lQGNvbGxhYm9yYS5jb20+iJkEExYKAEECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4 AWIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaCyyxgUJCWX3dQAKCRDZQZRRKWBy9ARJAP96pFmLffZ smBUpkyVBfFAf+zq6BJt769R0al3kHvUKdgD9G7KAHuioxD2v6SX7idpIazjzx8b8rfzwTWyOQWHC AAS0LU5pY29sYXMgRHVmcmVzbmUgPG5pY29sYXMuZHVmcmVzbmVAZ21haWwuY29tPoiZBBMWCgBBF iEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrGYCGwMFCQll93UFCwkIBwICIgIGFQoJCAsCBBYCAw ECHgcCF4AACgkQ2UGUUSlgcvRObgD/YnQjfi4+L8f4fI7p1pPMTwRTcaRdy6aqkKEmKsCArzQBAK8 bRLv9QjuqsE6oQZra/RB4widZPvphs78H0P6NmpIJ Organization: Collabora Canada Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-xFHKxA+aWyg4BdbVGHsJ" User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 --=-xFHKxA+aWyg4BdbVGHsJ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Le jeudi 12 f=C3=A9vrier 2026 =C3=A0 11:23 -0500, Detlev Casanova a =C3=A9c= rit=C2=A0: > These fields will be used in traces to help userspace tracing tools > identify streams. >=20 > The tgid field will keep the PID of the process that opened the video > file. > That is needed because trace calls can happen in IRQs, for which there is > no current PID. >=20 > The fd field helps identify the context in case the same process opens th= e > video device multiple times. > Note that the fd field is set in the __video_do_ioctl() function. > That is because the file descriptor has not been allocated yet when > v4l2_open() is called. Unless someone have a better idea with this last part (in this case please reply): Reviewed-by: Nicolas Dufresne >=20 > Signed-off-by: Detlev Casanova > --- > =C2=A0drivers/media/v4l2-core/v4l2-fh.c=C2=A0=C2=A0=C2=A0 |=C2=A0 1 + > =C2=A0drivers/media/v4l2-core/v4l2-ioctl.c | 17 +++++++++++++++++ > =C2=A0include/media/v4l2-fh.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 4 ++++ > =C2=A03 files changed, 22 insertions(+) >=20 > diff --git a/drivers/media/v4l2-core/v4l2-fh.c b/drivers/media/v4l2-core/= v4l2- > fh.c > index df3ba9d4674b..86e8223b46cb 100644 > --- a/drivers/media/v4l2-core/v4l2-fh.c > +++ b/drivers/media/v4l2-core/v4l2-fh.c > @@ -37,6 +37,7 @@ void v4l2_fh_init(struct v4l2_fh *fh, struct video_devi= ce > *vdev) > =C2=A0 INIT_LIST_HEAD(&fh->available); > =C2=A0 INIT_LIST_HEAD(&fh->subscribed); > =C2=A0 fh->sequence =3D -1; > + fh->tgid =3D current->tgid; > =C2=A0 mutex_init(&fh->subscribe_lock); > =C2=A0} > =C2=A0EXPORT_SYMBOL_GPL(v4l2_fh_init); > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2- > core/v4l2-ioctl.c > index 37d33d4a363d..a3b6df0571d6 100644 > --- a/drivers/media/v4l2-core/v4l2-ioctl.c > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c > @@ -9,6 +9,7 @@ > =C2=A0 */ > =C2=A0 > =C2=A0#include > +#include > =C2=A0#include > =C2=A0#include > =C2=A0#include > @@ -3061,6 +3062,16 @@ void v4l_printk_ioctl(const char *prefix, unsigned= int > cmd) > =C2=A0} > =C2=A0EXPORT_SYMBOL(v4l_printk_ioctl); > =C2=A0 > +static int _file_iterate(const void *priv, struct file *filp, unsigned i= nt > fd) > +{ > + const struct file *fh_filp =3D priv; > + > + if (fh_filp =3D=3D filp) > + return fd; > + > + return 0; > +} > + > =C2=A0static long __video_do_ioctl(struct file *file, > =C2=A0 unsigned int cmd, void *arg) > =C2=A0{ > @@ -3081,6 +3092,12 @@ static long __video_do_ioctl(struct file *file, > =C2=A0 return ret; > =C2=A0 } > =C2=A0 > + if (unlikely(!vfh->fd)) { > + vfh->fd =3D iterate_fd(current->files, 0, _file_iterate, file); > + if (!vfh->fd) > + vfh->fd =3D -1; > + } > + > =C2=A0 /* > =C2=A0 * We need to serialize streamon/off with queueing new requests. > =C2=A0 * These ioctls may trigger the cancellation of a streaming > diff --git a/include/media/v4l2-fh.h b/include/media/v4l2-fh.h > index aad4b3689d7e..4ef4e58ab8d1 100644 > --- a/include/media/v4l2-fh.h > +++ b/include/media/v4l2-fh.h > @@ -28,6 +28,8 @@ struct v4l2_ctrl_handler; > =C2=A0 * @vdev: pointer to &struct video_device > =C2=A0 * @ctrl_handler: pointer to &struct v4l2_ctrl_handler > =C2=A0 * @prio: priority of the file handler, as defined by &enum v4l2_pr= iority > + * @tgid: process id that initialized the v4l2_fh > + * @fd: file descriptor associated to this v4l2_fh for the process id in= tgid > =C2=A0 * > =C2=A0 * @wait: event' s wait queue > =C2=A0 * @subscribe_lock: serialise changes to the subscribed list; guara= ntee that > @@ -44,6 +46,8 @@ struct v4l2_fh { > =C2=A0 struct video_device *vdev; > =C2=A0 struct v4l2_ctrl_handler *ctrl_handler; > =C2=A0 enum v4l2_priority prio; > + uint32_t tgid; > + int fd; > =C2=A0 > =C2=A0 /* Events */ > =C2=A0 wait_queue_head_t wait; --=-xFHKxA+aWyg4BdbVGHsJ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCafELGQAKCRDZQZRRKWBy 9AKXAP4kExFAk5kv4T+O4pPqDHiq2EYtpPeu4d74JPDJHJgK1wEAhL3jwZnj2C09 fdBkWR/kS74Jwd1c58A6367FMwwOggY= =4DUH -----END PGP SIGNATURE----- --=-xFHKxA+aWyg4BdbVGHsJ--