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 1B89DCF9C70 for ; Mon, 23 Sep 2024 14:22:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 963ED10E3FC; Mon, 23 Sep 2024 14:22:39 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="V8cM5Mlh"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7232610E3FC; Mon, 23 Sep 2024 14:22:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1727101359; x=1758637359; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=T07yc8YMoGWIJ8Xl3YnxsD3q6bRlLgSgHV4rCZS8UQE=; b=V8cM5MlhVF/RZoRVeRin7MCpRZBip3RzNjzcJOz2YHWKqjY1CjuAKVbW MdxadxDCkMbLPeh7SPUHnRwMrDgZ0PJMf0oQlZ/NO0t0lI/23q6YdD/XL w72zh8oR7OOsX1dWsiIIG434UYGIv0+Yx5btdeBucA45Kt1JtzA8TIomJ yy/7uaY4Ca1u+9tEcy3yUhkbrieu2/u61zP7v5tlLDGcnOXa8ZG4c/u5S 8lpvJ+kNsBRN0gGiBJqtUeK4HvbvNqgGpkNnfptEbmjcaIfS9Lj7eOHIT sld8So6bw1Hb5teoM2NuovXJ6Bh7vLhvoalkDw6ptb/uvGsopd/3NLEXn A==; X-CSE-ConnectionGUID: LzbYtQUbQRiTV+3z427XJw== X-CSE-MsgGUID: uTNR59NyRK2yjv1Y9A7JUA== X-IronPort-AV: E=McAfee;i="6700,10204,11204"; a="37427107" X-IronPort-AV: E=Sophos;i="6.10,251,1719903600"; d="scan'208";a="37427107" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Sep 2024 07:22:38 -0700 X-CSE-ConnectionGUID: cK/S3Z6rSTyaay29UuJ68A== X-CSE-MsgGUID: 4dqQpE72RYyxqrkxrl7APA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.10,251,1719903600"; d="scan'208";a="71227620" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.74]) by fmviesa008.fm.intel.com with SMTP; 23 Sep 2024 07:22:35 -0700 Received: by stinkbox (sSMTP sendmail emulation); Mon, 23 Sep 2024 17:22:34 +0300 Date: Mon, 23 Sep 2024 17:22:34 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jani Nikula Cc: intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org Subject: Re: [PATCH 4/5] drm/i915/bios: Extract vbt_signature[] Message-ID: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87frpq7myg.fsf@intel.com> X-Patchwork-Hint: comment 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, Sep 23, 2024 at 12:12:39PM +0300, Jani Nikula wrote: > On Fri, 20 Sep 2024, Ville Syrjälä wrote: > > On Thu, Sep 12, 2024 at 03:15:52PM +0300, Jani Nikula wrote: > >> On Tue, 10 Sep 2024, Ville Syrjala wrote: > >> > From: Ville Syrjälä > >> > > >> > Replace the three hand rolled "$VBT"s with a vbt_signature[] > >> > to avoid accidents. > >> > > >> > Signed-off-by: Ville Syrjälä > >> > --- > >> > drivers/gpu/drm/i915/display/intel_bios.c | 12 +++++++++--- > >> > 1 file changed, 9 insertions(+), 3 deletions(-) > >> > > >> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c > >> > index cbbda94c3dab..0b92b494117f 100644 > >> > --- a/drivers/gpu/drm/i915/display/intel_bios.c > >> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c > >> > @@ -2964,6 +2964,8 @@ static const struct bdb_header *get_bdb_header(const struct vbt_header *vbt) > >> > return _vbt + vbt->bdb_offset; > >> > } > >> > > >> > +static const char vbt_signature[4] = "$VBT"; > >> > >> 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[] = { '$', 'V', 'B', 'T' }; > > ? > > Alternatively, > > static const char *vbt_signature = "$VBT"; Or could just be something like: static const char vbt_signature[] = "$VBT"; static const int vbt_signature_len = 4; BUILD_BUG_ON(vbt_signature_len != sizeof(vbt_signature) - 1); BUILD_BUG_ON(vbt_signature_len != sizeof(u32)); and use vbt_signature_len instead sizeof(vbt_signature) everwhere. > > > > >> Reviewed-by: Jani Nikula > >> > >> > >> > + > >> > /** > >> > * intel_bios_is_valid_vbt - does the given buffer contain a valid VBT > >> > * @display: display device > >> > @@ -2986,7 +2988,7 @@ bool intel_bios_is_valid_vbt(struct intel_display *display, > >> > return false; > >> > } > >> > > >> > - if (memcmp(vbt->signature, "$VBT", 4)) { > >> > + if (memcmp(vbt->signature, vbt_signature, sizeof(vbt_signature))) { > > But then this would need strlen() > > >> > 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 = intel_uncore_read(&i915->uncore, OROM_OFFSET); > >> > oprom_offset &= OROM_OFFSET_MASK; > >> > > >> > + BUILD_BUG_ON(sizeof(vbt_signature) != sizeof(u32)); > > And maybe this could be sizeof(vbt_signature) < sizeof(u32) > > All of the alternatives are a bit disappointing, so maybe let's just > roll with the patch you already have here? > > BR, > Jani. > > >> > + > >> > for (count = 0; count < oprom_size; count += 4) { > >> > data = intel_spi_read32(&i915->uncore, oprom_offset + count); > >> > - if (data == *((const u32 *)"$VBT")) { > >> > + if (data == *((const u32 *)vbt_signature)) { > >> > found = oprom_offset + count; > >> > break; > >> > } > >> > @@ -3144,9 +3148,11 @@ static struct vbt_header *oprom_get_vbt(struct intel_display *display, > >> > if (!oprom) > >> > return NULL; > >> > > >> > + BUILD_BUG_ON(sizeof(vbt_signature) != sizeof(u32)); > >> > + > >> > /* Scour memory looking for the VBT signature. */ > >> > for (i = 0; i + 4 < size; i += 4) { > >> > - if (ioread32(oprom + i) != *((const u32 *)"$VBT")) > >> > + if (ioread32(oprom + i) != *((const u32 *)vbt_signature)) > >> > continue; > >> > > >> > p = oprom + i; > >> > >> -- > >> Jani Nikula, Intel > > -- > Jani Nikula, Intel -- Ville Syrjälä Intel