Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754707AbaFNMgA (ORCPT ); Sat, 14 Jun 2014 08:36:00 -0400 Received: from hygieia.santi-shop.eu ([78.46.175.2]:36123 "EHLO hygieia.santi-shop.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754643AbaFNMf6 (ORCPT ); Sat, 14 Jun 2014 08:35:58 -0400 Date: Sat, 14 Jun 2014 14:35:50 +0200 From: Bruno =?UTF-8?B?UHLDqW1vbnQ=?= To: Stefan Biereigel Cc: linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-console@vger.kernel.org, brian Subject: Re: console / fbdev: fbcon support for bits_per_pixel = 1? Message-ID: <20140614143550.59367463@neptune.home> In-Reply-To: <539C1C1F.5060904@biereigel.de> References: <539C1C1F.5060904@biereigel.de> X-Mailer: Claws Mail 3.9.0 (GTK+ 2.24.23; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Stefan, On Sat, 14 June 2014 Stefan Biereigel wrote: > CC: linux-console, linux-fbdev > > Hello Kernel Developers, > for a university assignment we are developing a frame buffer driver for a monochrome > display. We succeeded so far in making a simple "RAM frame buffer" module, which is needed > as the basis (we don't have read access to the RAM in the LCD). > We are using the system-default fb_ops (fb_sys_{read,write}, > sys_{fillrect,copyarea,imageblit), and all is well when we use bits_per_pixel = 8. When we > map a console to the RAM frame buffer (con2fbmap 1 1), do strg-alt-F1, type some > characters there, we can then 'cat /dev/fb1' and plot the ram contents in Matlab > (reshaping the data to be our display geometry first), where our typed characters and the > console appear. > > If we however change bits_per_pixel to 1, and divide line_length by 8 (as it should > represent the line length in bytes), this suddenly stops working: echo and cat to fb1 work > as intended: We change our Matlab-Script to interpret every byte as 8 pixels, bytes > written into /dev/fb1 can be read out correctly. If we however map the console to fb1, no > console output can be seen in RAM - it is (seemingly) filled with garbage. > > We're using fbcon as the console driver, and the first frame buffer for me is intelfb. I > see, that the bitblitting-calls for every typed character are depth 1 and have correct > geometry, but the whole bitblitting-builtin seems not to work for bits_per_pixel = 1, i > tried it with a simple test image after the initialisation... > > Is this behavior intended or are we triggering a bug here (that no one noticed, because > who in the world uses monochrome framebuffers these days..). I can't see any comments that > monochrome consoles should not work with 1 bit per pixel. See the code below if you spot > some errors (ignore some missing error handling and mediocre style for now, please). fbcon on 1bpp frambuffer worked for me with picoLCD (though I have found no userspace framebuffer application willing to operate at 1bpp). Thus I allow for 1bpp or 8bpp and convert 8bpp to 1bpp for the picolcd. As for your case, picoLCD is "write-only" monochrome LCD backed by in-RAM shadow framebuffer. (see drivers/hid/hid-picolcd_fb.c) Bruno > Thank you for any help and input. > Best regards, > Stefan Biereigel > > 8<--- testfb.c > > #include > #include > > #include > #include > #include > #include > #include > > #define DISPLAY_WIDTH 240 > #define DISPLAY_HEIGHT 64 > #define FB_MEM_SIZE (DISPLAY_WIDTH * DISPLAY_HEIGHT)/8 > > static struct platform_device *testfb_device; > > static struct fb_ops fbops = { > .owner = THIS_MODULE, > .fb_fillrect = sys_fillrect, > .fb_copyarea = sys_copyarea, > .fb_imageblit = sys_imageblit, > .fb_read = fb_sys_read, > .fb_write = fb_sys_write, > .fb_sync = NULL, > }; > > static int __init testfb_probe (struct platform_device *pdev) { > void *fb_mem = NULL; > struct fb_info *fbinfo = NULL; > > fb_mem = kzalloc(FB_MEM_SIZE, GFP_KERNEL); > > if (!fb_mem) { > pr_err("testfb: memory allocation for framebuffer failed\n"); > return(-ENOMEM); > } > else > pr_debug("testfb: allocated framebuffer memory successfully\n"); > > fbinfo = framebuffer_alloc(0, &pdev->dev); > > if (!fbinfo) { > pr_err("testfb: framebuffer_alloc() failed\n"); > kfree(fb_mem); > return(-1); > } > else > pr_debug("testfb: framebuffer_alloc was successful\n"); > > fbinfo->fix.smem_start = (unsigned long) fb_mem; > fbinfo->screen_base = (char __iomem *) fb_mem; > fbinfo->fix.smem_len = FB_MEM_SIZE; > fbinfo->fbops = &fbops; > > fbinfo->node = 0; /* ?int */ > fbinfo->device = &pdev->dev; > fbinfo->flags = FBINFO_DEFAULT; /* */ > fbinfo->var.xres = DISPLAY_WIDTH; /* visible resolution */ > fbinfo->var.yres = DISPLAY_HEIGHT; /* visible resolution */ > fbinfo->var.xres_virtual = DISPLAY_WIDTH; /* virtual resolution */ > fbinfo->var.yres_virtual = DISPLAY_HEIGHT; /* virtual resolution */ > fbinfo->var.bits_per_pixel = 1; /* bits per pixel */ > fbinfo->var.activate = FB_ACTIVATE_NOW; /* set values immediately (or vbl) */ > fbinfo->var.sync = 0; /* ?see FB_SYNC_* */ > fbinfo->var.vmode = FB_VMODE_NONINTERLACED; /* non interlaced, see FB_VMODE_* */ > fbinfo->var.left_margin = 0; > fbinfo->var.right_margin = 0; > fbinfo->var.upper_margin = 0; > fbinfo->var.lower_margin = 0; > fbinfo->var.red.offset = 0; > fbinfo->var.red.length = fbinfo->var.bits_per_pixel; > fbinfo->var.green = fbinfo->var.red; > fbinfo->var.blue = fbinfo->var.red; > fbinfo->var.grayscale = 1; > strcpy(fbinfo->fix.id, "testfb"); /* identifier, 16 byte */ > fbinfo->fix.type = FB_TYPE_PACKED_PIXELS; /* pack pixels to avoid overhead */ > fbinfo->fix.visual = FB_VISUAL_MONO10; /* Monochr. 1=Black 0=White */ > fbinfo->fix.line_length = DISPLAY_WIDTH/8; /* length of a line in bytes */ > fbinfo->fix.accel = FB_ACCEL_NONE; /* no hardware accelerator */ > fbinfo->fix.xpanstep = 0; > fbinfo->fix.ypanstep = 0; > fbinfo->fix.ywrapstep = 0; > > if (register_framebuffer(fbinfo) < 0) { > pr_err("testfb: registering framebuffer failed\n"); > kfree((void *) fbinfo->fix.smem_start); > framebuffer_release(fbinfo); > return(-1); > } > else > pr_debug("testfb: registered framebuffer\n"); > > platform_set_drvdata(pdev, fbinfo); > > return 0; > } > > static int testfb_remove(struct platform_device *pdev) { > struct fb_info *fbinfo = NULL; > > fbinfo = platform_get_drvdata(pdev); > > if (!fbinfo) { > pr_err("testfb: unable to get fbinfo from pdev\n"); > return(-1); > } > > if (unregister_framebuffer(fbinfo) < 0) > pr_err("testfb: unregistering framebuffer failed\n"); > else > pr_debug("testfb: unregistered framebuffer\n"); > > kfree((void *) fbinfo->fix.smem_start); > > framebuffer_release(fbinfo); > > return 0; > } > > static struct platform_driver testfb_driver = { > .probe = testfb_probe, > .remove = testfb_remove, > .driver = { > .name = "testfb", > }, > }; > > static int __init testfb_init(void) > { > int ret; > > ret = platform_driver_register(&testfb_driver); > if (!ret) { > testfb_device = platform_device_register_simple("testfb", 0, > NULL, 0); > > if (IS_ERR(testfb_device)) { > platform_driver_unregister(&testfb_driver); > ret = PTR_ERR(testfb_device); > } else { > pr_info("testfb: platform_device registered\n"); > } > > } > > pr_info("testfb: module loaded\n"); > > return 0; > } > > static void __exit testfb_exit(void) > { > platform_device_unregister(testfb_device); > platform_driver_unregister(&testfb_driver); > > pr_info("testfb: module unloaded\n"); > } > > module_init(testfb_init); > module_exit(testfb_exit); > > MODULE_LICENSE("GPL v2"); > MODULE_ALIAS("testfb"); > MODULE_AUTHOR("Brian Fonfara"); > MODULE_DESCRIPTION("Ein Modul zum Test der Linux Framebuffer-Programmierung"); > MODULE_DESCRIPTION("version 0.1"); > -- > To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/