详解linux lcd驱动编写

玛丽要骑大摩托 發表於 2023-6-9 00:00:00

<p>
有些嵌入式设备是不需要lcd的，比如路由器。但是，还有些设备是需要lcd显示内容的，比如游戏机、测试仪、智能手表等等。所以，今天我们就看看lcd驱动在linux上是怎么进行的。</p>
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1、代码目录</p>
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<code class="plain plain">drivers/video</code>
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2、查看video下的Makefile文件</p>
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<code class="plain plain"># SPDX-License-Identifier: GPL-2.0</code>
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<code class="plain plain">obj-$(CONFIG_VGASTATE)      += vgastate.o</code>
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<code class="plain plain">obj-$(CONFIG_HDMI)        += hdmi.o</code>
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<code class="plain plain">obj-$(CONFIG_VT) += console/</code>
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<code class="plain plain">obj-$(CONFIG_FB_STI) += console/</code>
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<code class="plain plain">obj-$(CONFIG_LOGO) += logo/</code>
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<code class="plain plain">obj-y   += backlight/</code>
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<code class="plain plain">obj-y   += fbdev/</code>
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<code class="plain plain">obj-$(CONFIG_VIDEOMODE_HELPERS) += display_timing.o videomode.o</code>
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<code class="plain plain">ifeq ($(CONFIG_OF),y)</code>
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<code class="plain plain">obj-$(CONFIG_VIDEOMODE_HELPERS) += of_display_timing.o of_videomode.o</code>
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<code class="plain plain">endif</code>
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3、fbdev默认是被编译的，一般情况下我们只需要看这个目录就行了</p>
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<code class="plain plain">config FB_S3C2410</code>
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<code class="plain spaces"> </code><code class="plain plain">tristate "S3C2410 LCD framebuffer support"</code>
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<code class="plain spaces"> </code><code class="plain plain">depends on FB && ARCH_S3C24XX</code>
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<code class="plain spaces"> </code><code class="plain plain">select FB_CFB_FILLRECT</code>
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<code class="plain spaces"> </code><code class="plain plain">select FB_CFB_COPYAREA</code>
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<code class="plain spaces"> </code><code class="plain plain">select FB_CFB_IMAGEBLIT</code>
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<code class="plain spaces"> </code><code class="plain plain">---help---</code>
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<code class="plain spaces">  </code><code class="plain plain">Frame buffer driver for the built-in LCD controller in the Samsung</code>
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<code class="plain spaces">  </code><code class="plain plain">S3C2410 processor.</code>
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<code class="plain spaces">  </code><code class="plain plain">This driver is also available as a module ( = code which can be</code>
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<code class="plain spaces">  </code><code class="plain plain">inserted and removed from the running kernel whenever you want). The</code>
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<code class="plain spaces">  </code><code class="plain plain">module will be called s3c2410fb. If you want to compile it as a module,</code>
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<code class="plain spaces">  </code><code class="plain plain">say M here and read <file:Documentation/kbuild/modules.txt>.</code>
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<code class="plain spaces">  </code><code class="plain plain">If unsure, say N.</code>
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<code class="plain plain">config FB_S3C2410_DEBUG</code>
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<code class="plain spaces"> </code><code class="plain plain">bool "S3C2410 lcd debug messages"</code>
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<code class="plain spaces"> </code><code class="plain plain">depends on FB_S3C2410</code>
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<code class="plain spaces"> </code><code class="plain plain">help</code>
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<code class="plain spaces">  </code><code class="plain plain">Turn on debugging messages. Note that you can set/unset at run time</code>
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<code class="plain spaces">  </code><code class="plain plain">through sysfs</code>
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4、以s3c2410为例，分析得出其lcd主要依赖的macro是FB_S3C2410,</p>
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<code class="plain plain">obj-y += core/</code>
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<code class="plain plain">obj-$(CONFIG_FB_S3C2410) += s3c2410fb.o</code>
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5、除了core是默认编译的，我们只需要查看s3c2410fb.c这个文件</p>
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<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">platform_driver s3c2410fb_driver = {</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.probe = s3c2410fb_probe,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.</code><code class="cpp functions bold">remove</code> <code class="cpp plain">= s3c2410fb_remove,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.suspend = s3c2410fb_suspend,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.resume = s3c2410fb_resume,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.driver = {</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.name = </code><code class="cpp string">"s3c2410-lcd"</code><code class="cpp plain">,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">},</code>
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<code class="cpp plain">};</code>
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<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">platform_driver s3c2412fb_driver = {</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.probe = s3c2412fb_probe,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.</code><code class="cpp functions bold">remove</code> <code class="cpp plain">= s3c2410fb_remove,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.suspend = s3c2410fb_suspend,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.resume = s3c2410fb_resume,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.driver = {</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.name = </code><code class="cpp string">"s3c2412-lcd"</code><code class="cpp plain">,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">},</code>
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<code class="cpp plain">};</code>
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<code class="cpp color1 bold">int</code> <code class="cpp plain">__init s3c2410fb_init(</code><code class="cpp keyword bold">void</code><code class="cpp plain">)</code>
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<code class="cpp plain">{</code>
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<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">ret = platform_driver_register(&s3c2410fb_driver);</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(ret == 0)</code>
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<code class="cpp spaces"> </code><code class="cpp plain">ret = platform_driver_register(&s3c2412fb_driver);</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">ret;</code>
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<code class="cpp plain">}</code>
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<p>
6、不出意外，这又是一个platform设备，接着看看其probe函数做了什么</p>
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<code class="cpp plain">ret = register_framebuffer(fbinfo);</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(ret < 0) {</code>
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<code class="cpp spaces"> </code><code class="cpp plain">dev_err(&pdev->dev, </code><code class="cpp string">"Failed to register framebuffer device: %d\n"</code><code class="cpp plain">,</code>
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<code class="cpp spaces">  </code><code class="cpp plain">ret);</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">goto</code> <code class="cpp plain">free_cpufreq;</code>
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<code class="cpp spaces"> </code><code class="cpp plain">}</code>
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<p>
7、整个代码，最重要的就是这个register动作，当然还要阅读一下是否存在其他的函数接口</p>
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<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">fb_ops s3c2410fb_ops = {</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.owner = THIS_MODULE,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.fb_check_var = s3c2410fb_check_var,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.fb_set_par = s3c2410fb_set_par,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.fb_blank = s3c2410fb_blank,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.fb_setcolreg = s3c2410fb_setcolreg,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.fb_fillrect = cfb_fillrect,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.fb_copyarea = cfb_copyarea,</code>
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<code class="cpp spaces"> </code><code class="cpp plain">.fb_imageblit = cfb_imageblit,</code>
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<code class="cpp plain">};</code>
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<p>
8、最后还是老规矩，看看有没有中断需要处理的</p>
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<code class="cpp plain">ret = request_irq(irq, s3c2410fb_irq, 0, pdev->name, info);</code>
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<p>
9、后面的话</p>
<p>
很多同学把驱动想的很复杂，其实都是一些格式代码。掌握了基本结构，加上芯片手册、硬件协议，一般的驱动都可以在很短的时间内学会，这个不存在问题。尤其是那些在市场上出现了很多年的soc，基本不需要改动就可以直接使用。当然，如果真的发现问题了，我们也要有debug的能力。drivers目录里面的内容很多，但是需要了解和关心的其实不多，努力去做、去解决问题就可以了。</p>
<p>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。</p>
<p>
原文链接：https://blog.csdn.net/feixiaoxing/article/details/79885576</p>

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详解linux lcd驱动编写