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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 32F96CF9C70 for ; Mon, 23 Sep 2024 14:24:54 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D24B710E240; Mon, 23 Sep 2024 14:24:53 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="FqZ88JBU"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4BACD10E240; Mon, 23 Sep 2024 14:24:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1727101492; x=1758637492; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version:content-transfer-encoding; bh=cBN6bZs8gxWRhGxp/HDxJVmBIsHD9XBAO7gZyrKPF+w=; b=FqZ88JBU9oNfZCx8qet+oPGW8hrNxzPJELw+qEzeqKonyaw6xog5DsS1 MfhEu+Dl37tPulGlLqAVqEjMk87I/yUnvV76w0HH5thtP/JHeowhG1z9r 9HcATYmffggPmhSd+JSyxf6xanNGSLCYmFA2IlOUim/cO9M8eNUMu/siY jyFtY1LVKO5SSmtfx0jYIzMd7zRB4J3CFjwgSffi+4N66Agc4ZyUjmKhk ElEBpEF2sXOYuMqPIPG4WxfOih0j4uJ3eNJSOXkOhaVJm2c8HWuQ3Gyyr A4B7moLgACBHriDdIl3d3xOWgBso280ZEqDUKhhWcaf/bqmP3WlQTIbwX g==; X-CSE-ConnectionGUID: eR2oc51DQoylWrkGgqoB7w== X-CSE-MsgGUID: /ZftSNNSRKuDqdjnSUTZ3A== X-IronPort-AV: E=McAfee;i="6700,10204,11204"; a="29773715" X-IronPort-AV: E=Sophos;i="6.10,251,1719903600"; d="scan'208";a="29773715" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Sep 2024 07:24:52 -0700 X-CSE-ConnectionGUID: yNkYwKeIRxq36lwU9Qd/Fg== X-CSE-MsgGUID: 6EjDxhlXTnCu+lPcvm7Myg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.10,251,1719903600"; d="scan'208";a="108520826" Received: from sschumil-mobl2.ger.corp.intel.com (HELO localhost) ([10.245.246.65]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Sep 2024 07:24:49 -0700 From: Jani Nikula To: Ville =?utf-8?B?U3lyasOkbMOk?= Cc: intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org Subject: Re: [PATCH 4/5] drm/i915/bios: Extract vbt_signature[] In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20240910134219.28479-1-ville.syrjala@linux.intel.com> <20240910134219.28479-5-ville.syrjala@linux.intel.com> <87y13xf4p3.fsf@intel.com> <87frpq7myg.fsf@intel.com> Date: Mon, 23 Sep 2024 17:24:46 +0300 Message-ID: <877cb25txt.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Mon, 23 Sep 2024, Ville Syrj=C3=A4l=C3=A4 wrote: > On Mon, Sep 23, 2024 at 12:12:39PM +0300, Jani Nikula wrote: >> On Fri, 20 Sep 2024, Ville Syrj=C3=A4l=C3=A4 wrote: >> > On Thu, Sep 12, 2024 at 03:15:52PM +0300, Jani Nikula wrote: >> >> On Tue, 10 Sep 2024, Ville Syrjala wr= ote: >> >> > From: Ville Syrj=C3=A4l=C3=A4 >> >> > >> >> > Replace the three hand rolled "$VBT"s with a vbt_signature[] >> >> > to avoid accidents. >> >> > >> >> > Signed-off-by: Ville Syrj=C3=A4l=C3=A4 >> >> > --- >> >> > drivers/gpu/drm/i915/display/intel_bios.c | 12 +++++++++--- >> >> > 1 file changed, 9 insertions(+), 3 deletions(-) >> >> > >> >> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gp= u/drm/i915/display/intel_bios.c >> >> > index cbbda94c3dab..0b92b494117f 100644 >> >> > --- a/drivers/gpu/drm/i915/display/intel_bios.c >> >> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c >> >> > @@ -2964,6 +2964,8 @@ static const struct bdb_header *get_bdb_heade= r(const struct vbt_header *vbt) >> >> > return _vbt + vbt->bdb_offset; >> >> > } >> >> >=20=20 >> >> > +static const char vbt_signature[4] =3D "$VBT"; >> >>=20 >> >> Always a bit scary to add strings without termination, but I guess it= 's >> >> justified here. >> > >> > I guess we could make it look less like a string with eg. >> > static const u8 vbt_signature[] =3D { '$', 'V', 'B', 'T' }; >> > ? >>=20 >> Alternatively, >>=20 >> static const char *vbt_signature =3D "$VBT"; > > Or could just be something like: > > static const char vbt_signature[] =3D "$VBT"; > static const int vbt_signature_len =3D 4; > > BUILD_BUG_ON(vbt_signature_len !=3D sizeof(vbt_signature) - 1); > BUILD_BUG_ON(vbt_signature_len !=3D sizeof(u32)); > > and use vbt_signature_len instead sizeof(vbt_signature) everwhere. Works for me, up to you. BR, Jani. > >>=20 >> > >> >> Reviewed-by: Jani Nikula >> >>=20 >> >>=20 >> >> > + >> >> > /** >> >> > * intel_bios_is_valid_vbt - does the given buffer contain a valid= VBT >> >> > * @display: display device >> >> > @@ -2986,7 +2988,7 @@ bool intel_bios_is_valid_vbt(struct intel_dis= play *display, >> >> > return false; >> >> > } >> >> >=20=20 >> >> > - if (memcmp(vbt->signature, "$VBT", 4)) { >> >> > + if (memcmp(vbt->signature, vbt_signature, sizeof(vbt_signature)))= { >>=20 >> But then this would need strlen() >>=20 >> >> > drm_dbg_kms(display->drm, "VBT invalid signature\n"); >> >> > return false; >> >> > } >> >> > @@ -3082,9 +3084,11 @@ static struct vbt_header *spi_oprom_get_vbt(= struct intel_display *display, >> >> > oprom_offset =3D intel_uncore_read(&i915->uncore, OROM_OFFSET); >> >> > oprom_offset &=3D OROM_OFFSET_MASK; >> >> >=20=20 >> >> > + BUILD_BUG_ON(sizeof(vbt_signature) !=3D sizeof(u32)); >>=20 >> And maybe this could be sizeof(vbt_signature) < sizeof(u32) >>=20 >> All of the alternatives are a bit disappointing, so maybe let's just >> roll with the patch you already have here? >>=20 >> BR, >> Jani. >>=20 >> >> > + >> >> > for (count =3D 0; count < oprom_size; count +=3D 4) { >> >> > data =3D intel_spi_read32(&i915->uncore, oprom_offset + count); >> >> > - if (data =3D=3D *((const u32 *)"$VBT")) { >> >> > + if (data =3D=3D *((const u32 *)vbt_signature)) { >> >> > found =3D oprom_offset + count; >> >> > break; >> >> > } >> >> > @@ -3144,9 +3148,11 @@ static struct vbt_header *oprom_get_vbt(stru= ct intel_display *display, >> >> > if (!oprom) >> >> > return NULL; >> >> >=20=20 >> >> > + BUILD_BUG_ON(sizeof(vbt_signature) !=3D sizeof(u32)); >> >> > + >> >> > /* Scour memory looking for the VBT signature. */ >> >> > for (i =3D 0; i + 4 < size; i +=3D 4) { >> >> > - if (ioread32(oprom + i) !=3D *((const u32 *)"$VBT")) >> >> > + if (ioread32(oprom + i) !=3D *((const u32 *)vbt_signature)) >> >> > continue; >> >> >=20=20 >> >> > p =3D oprom + i; >> >>=20 >> >> --=20 >> >> Jani Nikula, Intel >>=20 >> --=20 >> Jani Nikula, Intel --=20 Jani Nikula, Intel