From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Antonino A. Daplas" Subject: Re: Problem with current fb_get_color_depth function Date: Mon, 11 Oct 2004 08:33:10 +0800 Sender: linux-kernel-owner@vger.kernel.org Message-ID: <200410110832.19978.adaplas@hotpop.com> References: <20041010225903.GA2418@darjeeling.triplehelix.org> Reply-To: adaplas@pol.net Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20041010225903.GA2418@darjeeling.triplehelix.org> Content-Disposition: inline List-Id: Cc: linux-kernel mailing list , linux-fbdev-devel@lists.sourceforge.net On Monday 11 October 2004 06:59, Joshua Kwan wrote: > because on advice from Andrew Suffield and Matthew Garrett the first > conditional was a roundabout way to check for grayscale displays, where > you can't actually have 24 bits (8 + 8 + 8) of gray. So it is suitable > to just return one of the values arbitrarily. But I noticed there was > also a grayscale variable, so I substituted that for the conditional > and my logo reappeared again :) > > So is radeonfb or fb_get_color_depth at fault here? Or was the logo > never appropriate for my display in the first place? (Unlikely, the > CLUT224 linux logo always displayed perfectly for me until now.) > This is because radeonfb chooses directcolor for its visual. With RGB565, the depth == 16, true. However, unlike truecolor where color values are hardwired to linear values, directcolor looks at the hardware CLUT. So, with directcolor RGB656, these are the CLUT lengths: Red and Blue = 32 (2 ^ 5) Green = 64 (2 ^ 6) (And you can see this in radeonfb_base:radeonfb_setcolreg()) if (rinfo->bpp == 16) { pindex = regno * 8; if (rinfo->depth == 16 && regno > 63) return 1; if (rinfo->depth == 15 && regno > 31) return 1; However, linux_logo_224 requires a CLUT with these lengths: Red = Green = Blue = 224; So, linux_logo_224 cannot be drawn when visual is directcolor at RGB555 or RGB565 because the logo clut requirements exceeds the hardware clut capability. You need to use a logo image with a lower depth such as the 16-color logo, linux_logo_16. In short, fb_get_color_depth() and radeonfb both do the correct thing, but you need a logo with a lower color depth. Or choose RGB888 or higher, or set the visual to truecolor. Tony PS: Note that this behavior is the same as 2.4 behavior (224-color logo is only chosen if directcolor and bpp >= 24). It might have worked before, and this is probably due to the directcolor clut being ramped to truecolor values. However, the correct solution is to use a 16-color logo.