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([2606:6d00:15:e06b::5ac]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-89ecb5cb14bsm89054306d6.1.2026.03.31.07.54.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2026 07:54:05 -0700 (PDT) Message-ID: <079b1630abe5dd22e032797fc12925c9c79ea305.camel@ndufresne.ca> Subject: Re: [RFC PATCH 1/7] media: v4l2-ctrls: Add V4L2_CID_MEMORY_USAGE control From: Nicolas Dufresne To: Frank Li , ming.qian@oss.nxp.com Cc: linux-media@vger.kernel.org, mchehab@kernel.org, hverkuil-cisco@xs4all.nl, sebastian.fricke@collabora.com, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, xiahong.bao@nxp.com, eagle.zhou@nxp.com, imx@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Date: Tue, 31 Mar 2026 10:54:03 -0400 In-Reply-To: References: <20260331072347.253-1-ming.qian@oss.nxp.com> <20260331072347.253-2-ming.qian@oss.nxp.com> Autocrypt: addr=nicolas@ndufresne.ca; prefer-encrypt=mutual; keydata=mDMEaCN2ixYJKwYBBAHaRw8BAQdAM0EHepTful3JOIzcPv6ekHOenE1u0vDG1gdHFrChD /e0J05pY29sYXMgRHVmcmVzbmUgPG5pY29sYXNAbmR1ZnJlc25lLmNhPoicBBMWCgBEAhsDBQsJCA cCAiICBhUKCQgLAgQWAgMBAh4HAheABQkJZfd1FiEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrjo CGQEACgkQ2UGUUSlgcvQlQwD/RjpU1SZYcKG6pnfnQ8ivgtTkGDRUJ8gP3fK7+XUjRNIA/iXfhXMN abIWxO2oCXKf3TdD7aQ4070KO6zSxIcxgNQFtDFOaWNvbGFzIER1ZnJlc25lIDxuaWNvbGFzLmR1Z nJlc25lQGNvbGxhYm9yYS5jb20+iJkEExYKAEECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4 AWIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaCyyxgUJCWX3dQAKCRDZQZRRKWBy9ARJAP96pFmLffZ smBUpkyVBfFAf+zq6BJt769R0al3kHvUKdgD9G7KAHuioxD2v6SX7idpIazjzx8b8rfzwTWyOQWHC AAS0LU5pY29sYXMgRHVmcmVzbmUgPG5pY29sYXMuZHVmcmVzbmVAZ21haWwuY29tPoiZBBMWCgBBF iEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrGYCGwMFCQll93UFCwkIBwICIgIGFQoJCAsCBBYCAw ECHgcCF4AACgkQ2UGUUSlgcvRObgD/YnQjfi4+L8f4fI7p1pPMTwRTcaRdy6aqkKEmKsCArzQBAK8 bRLv9QjuqsE6oQZra/RB4widZPvphs78H0P6NmpIJ Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-L4QS/jCTQxYv029Nq/FW" User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 --=-L4QS/jCTQxYv029Nq/FW Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Le mardi 31 mars 2026 =C3=A0 10:33 -0400, Frank Li a =C3=A9crit=C2=A0: > On Tue, Mar 31, 2026 at 03:23:11PM +0800, ming.qian@oss.nxp.com=C2=A0wrot= e: > > From: Ming Qian > >=20 > > Add a new read-only control V4L2_CID_MEMORY_USAGE that allows > > applications to query the total amount of memory currently used > > by a device instance. > >=20 > > This control reports the memory consumption in bytes, including > > internal buffers, intermediate processing data, and other > > driver-managed allocations. Applications can use this information > > for debugging, resource monitoring, or making informed decisions > > about buffer allocation strategies. > >=20 > > Signed-off-by: Ming Qian > > --- >=20 > Not sure why not export these information by debugfs, or any benefit vs > debugfs? There is also a on-going proposal that uses fdinfo. Nicolas >=20 > Generanlly document should be first patch, then driver change. >=20 > Frank >=20 > > =C2=A0drivers/media/v4l2-core/v4l2-ctrls-defs.c | 8 ++++++++ > > =C2=A0include/uapi/linux/v4l2-controls.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0 | 4 +++- > > =C2=A02 files changed, 11 insertions(+), 1 deletion(-) > >=20 > > diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/= v4l2-core/v4l2-ctrls-defs.c > > index 551426c4cd01..053db78ff661 100644 > > --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c > > +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c > > @@ -831,6 +831,7 @@ const char *v4l2_ctrl_get_name(u32 id) > > =C2=A0 case V4L2_CID_ALPHA_COMPONENT: return "Alpha Component"; > > =C2=A0 case V4L2_CID_COLORFX_CBCR: return "Color Effects, CbCr"; > > =C2=A0 case V4L2_CID_COLORFX_RGB:=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 return "Color Effects, RGB"; > > + case V4L2_CID_MEMORY_USAGE: return "Memory Usage"; > >=20 > > =C2=A0 /* > > =C2=A0 * Codec controls > > @@ -1476,6 +1477,13 @@ void v4l2_ctrl_fill(u32 id, const char **name, e= num v4l2_ctrl_type *type, > > =C2=A0 *min =3D 0; > > =C2=A0 *max =3D 0xffff; > > =C2=A0 break; > > + case V4L2_CID_MEMORY_USAGE: > > + *type =3D V4L2_CTRL_TYPE_INTEGER64; > > + *flags |=3D V4L2_CTRL_FLAG_READ_ONLY; > > + *min =3D 0; > > + *max =3D S64_MAX; > > + *step =3D 1; > > + break; > > =C2=A0 case V4L2_CID_FLASH_FAULT: > > =C2=A0 case V4L2_CID_JPEG_ACTIVE_MARKER: > > =C2=A0 case V4L2_CID_3A_LOCK: > > diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4= l2-controls.h > > index 68dd0c4e47b2..02c6f960d38e 100644 > > --- a/include/uapi/linux/v4l2-controls.h > > +++ b/include/uapi/linux/v4l2-controls.h > > @@ -110,8 +110,10 @@ enum v4l2_colorfx { > > =C2=A0#define V4L2_CID_COLORFX_CBCR (V4L2_CID_BASE+42) > > =C2=A0#define V4L2_CID_COLORFX_RGB (V4L2_CID_BASE+43) > >=20 > > +#define V4L2_CID_MEMORY_USAGE (V4L2_CID_BASE+44) > > + > > =C2=A0/* last CID + 1 */ > > -#define V4L2_CID_LASTP1=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=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 (V4L2_CID_BASE+44) > > +#define V4L2_CID_LASTP1=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=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 (V4L2_CID_BASE+45) > >=20 > > =C2=A0/* USER-class private control IDs */ > >=20 > > -- > > 2.53.0 > >=20 --=-L4QS/jCTQxYv029Nq/FW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCacvgCwAKCRDZQZRRKWBy 9HhiAP9pxmgO01Tw2u1jmX3JDGf0HUlwoJFHITjsspschCXhGwEA2CLSZfwaGF3P FBjvjpv8iG0M2472UaZ+ET35dRy4DwA= =NB0B -----END PGP SIGNATURE----- --=-L4QS/jCTQxYv029Nq/FW--