From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dmitry V. Levin" Subject: Re: [PATCH 2/4] drm: Add dispatcher and driver identification for DRM Date: Thu, 11 Jun 2015 02:26:59 +0300 Message-ID: <20150610232659.GA19231@altlinux.org> References: <1433849204-4125-1-git-send-email-patrik.jakobsson@linux.intel.com> <1433849204-4125-3-git-send-email-patrik.jakobsson@linux.intel.com> <20150609221420.GA3210@altlinux.org> <20150610115233.GA18221@rpjakobs-ThinkCentre-E73> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1687312045==" Return-path: Received: from pegasus3.altlinux.org (pegasus3.altlinux.org [194.107.17.103]) by gabe.freedesktop.org (Postfix) with ESMTP id A41F16E3E5 for ; Wed, 10 Jun 2015 16:27:01 -0700 (PDT) In-Reply-To: <20150610115233.GA18221@rpjakobs-ThinkCentre-E73> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: strace-devel@lists.sourceforge.net, intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org --===============1687312045== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="OXfL5xGRrasGEqWY" Content-Disposition: inline --OXfL5xGRrasGEqWY Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 10, 2015 at 01:52:33PM +0200, Patrik Jakobsson wrote: > On Wed, Jun 10, 2015 at 01:14:20AM +0300, Dmitry V. Levin wrote: > > On Tue, Jun 09, 2015 at 01:26:42PM +0200, Patrik Jakobsson wrote: [...] > > > +#define DRM_MAX_NAME_LEN 128 > > > + > > > +inline int drm_is_priv(const unsigned int num) > > > +{ > > > + return (_IOC_NR(num) >=3D DRM_COMMAND_BASE && > > > + _IOC_NR(num) < DRM_COMMAND_END); > > > +} > > > + > > > +static int drm_get_driver_name(struct tcb *tcp, char *name, size_t b= ufsize) > > > +{ > > > + char path[PATH_MAX]; > > > + char link[PATH_MAX]; > > > + int ret; > > > + > > > + ret =3D getfdpath(tcp, tcp->u_arg[0], path, PATH_MAX - 1); > > > + if (!ret) > > > + return ret; > > > + > > > + snprintf(link, PATH_MAX, "/sys/class/drm/%s/device/driver", > > > + basename(path)); > > > + > > > + ret =3D readlink(link, path, PATH_MAX - 1); > > > + if (ret < 0) > > > + return ret; > > > + > > > + path[ret] =3D '\0'; > > > + strncpy(name, basename(path), bufsize); > > > + > > > + return 0; > > > +} > > > + > > > +int drm_is_driver(struct tcb *tcp, const char *name) > > > +{ > > > + char drv[DRM_MAX_NAME_LEN]; > > > + int ret; > > > + > > > + ret =3D drm_get_driver_name(tcp, drv, DRM_MAX_NAME_LEN); > > > + if (ret) > > > + return 0; > > > + > > > + return strcmp(name, drv) =3D=3D 0; > > > +} > >=20 > > This interface will result to several getfdpath() calls per > > ioctl_decode(). If the only purpose of drm_is_driver() is to help find= ing > > the most appropriate function, let's create a table of pairs > > {driver name, function} and pass this table to a function that will do a > > single getfdpath() call, calculate the driver name, and choose the right > > function from the table. >=20 > Yes I was thinking the same thing but it's a bit tricky. What I need is: > fd -> path -> driver name. And fd -> path could change between ioctls. It= is not > a likely scenario but it's possible. I could get rid of the extra call in > drm_decode_number() if I put it back in drm_ioctl as in my RFC. I could a= lso > optimize path -> driver name with a table but I don't know how expensive = those > calls actually are. Not sure what would be the best solution here. drm_get_driver_name() is quite expensive as it does two readlink syscalls, so it should be called at most once per ioctl_decode(). Another method to achieve this is to change drm_get_driver_name() to return basename(path) instead of return code, so that drm_ioctl() would call it once and pass the result to strcmp calls: int drm_ioctl(struct tcb *tcp, const unsigned int code, long arg) { if (verbose(tcp) && drm_is_priv(code)) { const char *driver =3D drm_get_driver_name(tcp); if (!driver) return 0; if (!strcmp(driver, "i915")) return drm_i915_ioctl(tcp, code, arg); } return 0; } --=20 ldv --OXfL5xGRrasGEqWY Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlV4x8MACgkQfKvmrJ41Nh6u/QCeOtkv9+Ef90e04OK0Wj5Jgqpx j8AAoLJfv9J+W0J9lR8I6KFXjKqboVty =02kD -----END PGP SIGNATURE----- --OXfL5xGRrasGEqWY-- --===============1687312045== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KSW50ZWwtZ2Z4 IG1haWxpbmcgbGlzdApJbnRlbC1nZnhAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHA6Ly9saXN0 cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9saXN0aW5mby9pbnRlbC1nZngK --===============1687312045==--