QCom MSM平台显示屏Framebuffer设备注册过程
本文是Android Display部分分析的一部分，描述屏Framebuffer设备注册过程。
QC MSM7xxx/MSM8xxx平台本身就提供了很多接口的屏的支持，每种屏对应一个驱动文件。由于QC MSM平台显示驱动架构做了绝大部分的工作，驱动一块新的屏仅需要做很少量的工作。下面的过程是屏Framebuffer注册过程的分析。
设备资源申请是在MACHINE_DESC中实现的。示例如下：
3463MACHINE_START(MSM8930_CDP, "QCT MSM8930 CDP") 3464 .map_io = msm8930_map_io, 3465 .reserve = msm8930_reserve, 3466 .init_irq = msm8930_init_irq, 3467 .handle_irq = gic_handle_irq, 3468 .timer = &msm_timer, 3469 .init_machine = msm8930_cdp_init, 3470 .init_early = msm8930_allocate_memory_regions, 3471 .init_very_early = msm8930_early_memory, 3472 .restart = msm_restart, 3473MACHINE_END
machine_desc{.init_very_early, .init_early, .init_machine, .restart}, module_init driver的初始化顺序参考Machine_desc & boot & Kernel_init & initcall & module_init
在machine_desc.init中做了许多machine级别设备的注册工作，主要意图是做设备资源分配。该.init函数部分示例代码如下：
static void __init msm8930_cdp_init(void) @ kernel/arch/arm/mach-msm/board-8930.c
{
…
platform_add_devices(common_devices, ARRAY_SIZE(common_devices));
msm8930_init_gpu();
msm8930_init_mmc();
msm8930_init_cam();
msm8930_init_fb();
}
其中，msm8930_cdp_init中与display相关的是msm8930_init_fb()函数，这个函数注册了几个id为0的设备。各主要设备名如下，
“msm_fb” msm framebuffer设备，注意不是linux framebuffer设备，但是有对应关系；
“wfd” wifi显示设备；
“mipi_dsi_cmd_samsung_fwvga” mipi-dsi接口cmd模式LCD屏设备；
“hdmi_msm” HDMI显示器设备;
“mdp” mobile display station显示引擎设备；
“mipi-dsi” MIPI-DSI显示器驱动设备（id例外用了1，可能有的平台两个MIPI-DSI，另外一个id为0）；
1168void __init msm8930_init_fb(void) @ kernel/arch/arm/mach-msm/board-8930-display.c
1169{
1170 platform_device_register(&msm_fb_device);
1171
1172#ifdef CONFIG_FB_MSM_WRITEBACK_MSM_PANEL
1173 platform_device_register(&wfd_panel_device);
1174 platform_device_register(&wfd_device);
1175#endif
1176
1178#ifdef CONFIG_FB_MSM_MIPI_NOVATEK_CMD_QHD_PT
1179 platform_device_register(&mipi_dsi_novatek_panel_device);
1180#endif
1181
1184#ifdef CONFIG_FB_MSM_MIPI_SA77_CMD_FWVGA_PANEL
1185 platform_device_register(&mipi_dsi_cmd_chimei_fwvga_panel_device);
1186 platform_device_register(&mipi_dsi_cmd_samsung_fwvga_panel_device);
1187#endif
1189
1190#ifdef CONFIG_FB_MSM_HDMI_MSM_PANEL
1191 platform_device_register(&hdmi_msm_device);
1192#endif
1193
1194 platform_device_register(&mipi_dsi_toshiba_panel_device);
1195
1196 msm_fb_register_device("mdp", &mdp_pdata);
1197 msm_fb_register_device("mipi_dsi", &mipi_dsi_pdata);
1198#ifdef CONFIG_MSM_BUS_SCALING
1199#ifdef CONFIG_FB_MSM_DTV
1200 msm_fb_register_device("dtv", &dtv_pdata);
1201#endif
1202#endif
1203}
因为注册这些设备的意图主要是资源申请和初步初始化设备，所以各设备注册顺序并无关紧要。其初始化顺序还与后来的驱动实际注册顺序有关。
首先注册paltform_device msm_fb_device，该设备定义如下：
71static struct resource msm_fb_resources[] = {
72 {
73 .flags = IORESOURCE_DMA,
74 }
75};
135static struct msm_fb_platform_data msm_fb_pdata = {
136 .detect_client = msm_fb_detect_panel,
137};
138
139static struct platform_device msm_fb_device = {
140 .name = "msm_fb",
141 .id = 0,
142 .num_resources = ARRAY_SIZE(msm_fb_resources),
143 .resource = msm_fb_resources,
144 .dev.platform_data = &msm_fb_pdata,
145};
然后注册panel设备，定义如下：
845static struct mipi_dsi_panel_platform_data samsung_pdata = {
846 .enable_wled_bl_ctrl = 0x1,
847};
848
849static struct platform_device mipi_dsi_cmd_samsung_fwvga_panel_device = {
850 .name = "dsi_cmd_samsung_fwvga",
851 .id = 0,
852 .dev = {
853 .platform_data = &samsung_pdata,
854 }
855};
然后关键的注册mdp和mipi-dsi controller.
1749void __init msm_fb_register_device(char *name, void *data)
1750{
1751 if (!strncmp(name, "mdp", 3))
1752 msm_register_device(&msm_mdp_device, data);
1753 else if (!strncmp(name, "lcdc", 4))
1754 msm_register_device(&msm_lcdc_device, data);
1755 else if (!strncmp(name, "mipi_dsi", 8))
1756 msm_register_device(&msm_mipi_dsi_device, data);
1757#ifdef CONFIG_FB_MSM_TVOUT
1758 else if (!strncmp(name, "tvenc", 5))
1759 msm_register_device(&msm_tvenc_device, data);
1760 else if (!strncmp(name, "tvout_device", 12))
1761 msm_register_device(&msm_tvout_device, data);
1762#endif
1763#ifdef CONFIG_MSM_BUS_SCALING
1764 else if (!strncmp(name, "dtv", 3))
1765 msm_register_device(&msm_dtv_device, data);
1766#endif
1767 else
1768 printk(KERN_ERR "%s: unknown device! %s\n", __func__, name);
1769}
mdp和mipi-dsi设备及寄存器映射和中断需求如下
1484#define MIPI_DSI_HW_BASE 0x04700000
1485#define ROTATOR_HW_BASE 0x04E00000
1486#define TVENC_HW_BASE 0x04F00000
1487#define MDP_HW_BASE 0x05100000
1488
1489static struct resource msm_mipi_dsi_resources[] = {
1490 {
1491 .name = "mipi_dsi",
1492 .start = MIPI_DSI_HW_BASE,
1493 .end = MIPI_DSI_HW_BASE + 0x000F0000 - 1,
1494 .flags = IORESOURCE_MEM,
1495 },
1496 {
1497 .start = DSI_IRQ,
1498 .end = DSI_IRQ,
1499 .flags = IORESOURCE_IRQ,
1500 },
1501};
1502
1503static struct platform_device msm_mipi_dsi_device = {
1504 .name = "mipi_dsi",
1505 .id = 1,
1506 .num_resources = ARRAY_SIZE(msm_mipi_dsi_resources),
1507 .resource = msm_mipi_dsi_resources,
1508};
1509
1510static struct resource msm_mdp_resources[] = {
1511 {
1512 .name = "mdp",
1513 .start = MDP_HW_BASE,
1514 .end = MDP_HW_BASE + 0x000F0000 - 1,
1515 .flags = IORESOURCE_MEM,
1516 },
1517 {
1518 .start = INT_MDP,
1519 .end = INT_MDP,
1520 .flags = IORESOURCE_IRQ,
1521 },
1522};
1523
1524static struct platform_device msm_mdp_device = {
1525 .name = "mdp",
1526 .id = 0,
1527 .num_resources = ARRAY_SIZE(msm_mdp_resources),
1528 .resource = msm_mdp_resources,
1529};
以上设备注册时，其驱动并未加载，因为machine_desc.init_machine设备注册的arch_initcall是在.initcall3.init中，而module_init driver注册是在.initcall6.init中。等其驱动加载时，在对应的probe函数中，判断设备id，初步初始化设备，保存其资源分配。
此时，以下设备中id为0，mipi-dsi id为1的设备已经注册进系统了。
dsi_cmd_chimei_fwvga.0
dsi_cmd_samsung_fwvga.0
dsi_cmd_samsung_fwvga.1281
dtv.0
dtv.458753
hdmi_msm.0
hdmi_msm.1
mdp.0
mdp.458753
mdp.591105
mdp.655361
mipi_dsi.1
mipi_dsi.591105
mipi_toshiba.0
msm_fb.0
msm_fb.458753
msm_fb.591105
msm_fb.655361
下面描述各驱动注册，各驱动都是module_init的。
msm_fb驱动注册如下
module_init(msm_fb_init);
3898int __init msm_fb_init(void) @ kernel/drivers/video/msm/msm_fb.c
3899{
3900 int rc = -ENODEV;
3901
3902 if (msm_fb_register_driver())
3903 return rc;
….
}
3705static int msm_fb_register_driver(void)
3706{
3707 return platform_driver_register(&msm_fb_driver);
3708}
msm_fb_driver驱动定义如下
734static struct platform_driver msm_fb_driver = {
735 .probe = msm_fb_probe,
736 .remove = msm_fb_remove,
737#ifndef CONFIG_HAS_EARLYSUSPEND
738 .suspend = msm_fb_suspend,
739 .resume = msm_fb_resume,
740#endif
741 .shutdown = NULL,
742 .driver = {
743 /* Driver name must match the device name added in platform.c. */
744 .name = "msm_fb",
745 .pm = &msm_fb_dev_pm_ops,
746 },
747};
platform_device “msm_fb”的resource[0]是一块DMA内存，是framebuffer内存，但是在资源定义中并没有设置size，而在msm_fb_probe中从其使用可以看到该DMA内存已经分配。其size是在machine的init_early中从bootmem中分配的，比machine级别设备注册要早!
.init_early = msm8930_allocate_memory_regions,
msm8930_allocate_memory_regions(void) @ kernel/arch/arm/mach-msm/board-8930.c
1006static void __init msm8930_allocate_memory_regions(void)
1007{
1008 msm8930_allocate_fb_region();
1009}
msm8930_allocate_fb_region() @ kernel/arch/arm/mach-msm/board-8930-display.c
1205void __init msm8930_allocate_fb_region(void)
1206{
1207 void *addr;
1208 unsigned long size;
1209
1210 size = MSM_FB_SIZE;
1211 addr = alloc_bootmem_align(size, 0x1000);
1212 msm_fb_resources[0].start = __pa(addr);
1213 msm_fb_resources[0].end = msm_fb_resources[0].start + size - 1;
1214 pr_info("allocating %lu bytes at %p (%lx physical) for fb\n", size, addr, __pa(addr));
1216}
MSM_FB_SIZE宏定义如下，TRIPLE_BUFFER已是主流；对应地SurfaceFlinger中FB layer也会分配有3个buffer。
32#ifdef CONFIG_FB_MSM_TRIPLE_BUFFER
33#define MSM_FB_PRIM_BUF_SIZE \
34 (roundup((1920 * 1088 * 4), 4096) * 3) /* 4 bpp x 3 pages */
35#else
36#define MSM_FB_PRIM_BUF_SIZE \
37 (roundup((1920 * 1088 * 4), 4096) * 2) /* 4 bpp x 2 pages */
38#endif
39/* Note: must be multiple of 4096 */
40#define MSM_FB_SIZE roundup(MSM_FB_PRIM_BUF_SIZE, 4096)
当”msm_fb”注册时，msm_fb_probe在设备和驱动match后被调用。对于msm_fb_device id=0,只做fbram保存和ION client创建；这时probe到的设备对应/sys/bus/platform/devices /msm_fb.0。msm_ion_client_create(-1, pdev->name);”mipi-dsi” driver定义和注册如下 (in kernel/drivers/video/msm/mipi_dsi.c)
55static struct platform_driver mipi_dsi_driver = {
56 .probe = mipi_dsi_probe,
57 .remove = mipi_dsi_remove,
58 .shutdown = NULL,
59 .driver = {
60 .name = "mipi_dsi",
61 },
62};
603static int mipi_dsi_register_driver(void)
604{
605 return platform_driver_register(&mipi_dsi_driver);
606}
607
608static int __init mipi_dsi_driver_init(void)
609{
610 int ret;
611
612 mipi_dsi_init();
613
614 ret = mipi_dsi_register_driver();
615
616 device_initialize(&dsi_dev);
617
618 if (ret) {
619 pr_err("mipi_dsi_register_driver() failed!\n");
620 return ret;
621 }
622
623 return ret;
624}
625
626module_init(mipi_dsi_driver_init);
“mdp” driver定义和注册如下(in kernel/drivers/video/msm/mdp.c)
2094static struct platform_driver mdp_driver = {
2095 .probe = mdp_probe,
2096 .remove = mdp_remove,
2097#ifndef CONFIG_HAS_EARLYSUSPEND
2098 .suspend = mdp_suspend,
2099 .resume = NULL,
2100#endif
2101 .shutdown = NULL,
2102 .driver = {
2103 /*
2104 * Driver name must match the device name added in
2105 * platform.c.
2106 */
2107 .name = "mdp",
2108 .pm = &mdp_dev_pm_ops,
2109 },
2110};
3001static int mdp_register_driver(void)
3002{
3003#ifdef CONFIG_HAS_EARLYSUSPEND
3004 early_suspend.level = EARLY_SUSPEND_LEVEL_DISABLE_FB - 1;
3005 early_suspend.suspend = mdp_early_suspend;
3006 early_suspend.resume = mdp_early_resume;
3007 register_early_suspend(&early_suspend);
3008#endif
3009
3010 return platform_driver_register(&mdp_driver);
3011}
3012
3013static int __init mdp_driver_init(void)
3014{
3015 int ret;
3016
3017 mdp_drv_init();
3018
3019 ret = mdp_register_driver();
3020 if (ret) {
3021 printk(KERN_ERR "mdp_register_driver() failed!\n");
3022 return ret;
3023 }
3024
3025#if defined(CONFIG_DEBUG_FS)
3026 mdp_debugfs_init();
3027#endif
3028
3029 return 0;
3030
3031}
3032
3033module_init(mdp_driver_init);
当真正从屏驱动中添加一块显示设备时，为了让上级设备(“mipi-dsi” “mdp” “msm_fb” “fb”)使用下级设备，高通实现为下级设备创建了每个上级设备的实例，通过从下到上的设备probe链一级一级向上注册。这时保证从下到上的设备注册顺序就是至关重要的了，probe链做注册来保证这一点。
当然为了达到上级设备使用和管理下级设备的目标，另一种方法是下级设备向上级设备做register，这时要保证下级设备向上级设备注册时，上级设备的用于管理的相关数据结构已经准备好。
下面描述由屏驱动添加屏到注册linux framebuffer设备的流程。
在各自的屏设备注册文件中，会去探测屏，这种探测不是做真正扫描，仅仅是使用设备名字验证一下，以SAMSUNG MIPI DSI CMD屏为例，驱动会使用相应规则ID注册一块屏。
static int __init mipi_cmd_samsung_fwvga_pt_init(void) @ kernel/drivers/video/msm/mipi_samsung_cmd_fwvga_pt.c
{
37 int ret;
38
39 if (msm_fb_detect_client("mipi_cmd_samsung_fwvga"))
40 return 0;
……
88 ret = mipi_samsung_device_register(&pinfo, MIPI_DSI_PRIM, MIPI_DSI_PANEL_QHD_PT);
90 if (ret)
91 pr_err("%s: failed to register device!\n", __func__);
92
93 return ret;
94}
95
96module_init(mipi_cmd_samsung_fwvga_pt_init);
探测函数int msm_fb_detect_client(const char *name)首先使用主屏和外屏名字匹配，匹配不成则使用msm_fd_device.dev.platform .detect_client = msm_fb_detect_panel去匹配。上面欲同时注册SAMSUNG和CHIMEI两块屏设备，当然不能同时detect_panel成功，使用GPIO管脚配置做了二次匹配。实际不同批次的手机可能用到两块屏中的一种。
然后mipi_samsung_device_register()(对CHIMEI则是mipi_chimei_device_register)注册屏驱动和屏设备。驱动定义和注册具体如下，
358static struct platform_driver this_driver = {
359 .probe = mipi_samsung_lcd_probe,
360 .driver = {
361 .name = "dsi_cmd_samsung_fwvga",
362 },
363};
364
365static struct msm_fb_panel_data samsung_panel_data = {
366 .on = mipi_samsung_lcd_on,
367 .off = mipi_samsung_lcd_off,
368 .set_backlight = mipi_samsung_set_backlight,
369};
373int mipi_samsung_device_register(struct msm_panel_info *pinfo, u32 channel, u32 panel)
375{
376 struct platform_device *pdev = NULL;
377 int ret;
378
379 if ((channel >= 3) || ch_used[channel])
380 return -ENODEV;
381
382 ch_used[channel] = TRUE;
383
384 ret = mipi_samsung_lcd_init();
385 if (ret) {
386 pr_err("mipi_samsung_lcd_init() failed with ret %u\n", ret);
387 return ret;
388 }
389
390 pdev = platform_device_alloc("dsi_cmd_samsung_fwvga", (panel << 8)|channel);
391 if (!pdev)
392 return -ENOMEM;
393
394 samsung_panel_data.panel_info = *pinfo;
395
396 ret = platform_device_add_data(pdev, &samsung_panel_data,
397 sizeof(samsung_panel_data));
398 if (ret) {
399 printk(KERN_ERR
400 "%s: platform_device_add_data failed!\n", __func__);
401 goto err_device_put;
402 }
403
404 ret = platform_device_add(pdev);
405 if (ret) {
406 printk(KERN_ERR
407 "%s: platform_device_register failed!\n", __func__);
408 goto err_device_put;
409 }
410
411 return 0;
412
413err_device_put:
414 platform_device_put(pdev);
415 return ret;
416}
417
418static int mipi_samsung_lcd_init(void)
419{
420
421 led_trigger_register_simple("bkl_trigger", &bkl_led_trigger);
422 pr_info("%s: SUCCESS (WLED TRIGGER)\n", __func__);
423 wled_trigger_initialized = 1;
424
425 mipi_dsi_buf_alloc(&samsung_tx_buf, DSI_BUF_SIZE);
426 mipi_dsi_buf_alloc(&samsung_rx_buf, DSI_BUF_SIZE);
427
428 return platform_driver_register(&this_driver);
429}
在mipi_samsung_lcd_init()中注册platform_driver屏驱动，然后分配注册platform_device屏设备；platform_data设置为msm_fb_panel_data向上传递参数并用于上级设备调用控制屏开关和背光。
屏设备注册后，platform_device和platform_driver match,驱动的probe函数被调用，把参数一级一级向上带，用于设置上级设备参数，向上一级一级注册设备(“mipi-dsi”, “mdp”, “msm_fb”, “framebuffer”)。
一个类似的调用栈如下
------------[ cut here ]------------
WARNING: at /home/CORPUSERS/xp010548/myworkdroid/7x25a/LINUX/kernel/drivers/video/msm/msm_fb.c:1221 msm_fb_probe+0xf4/0xcbc()
msm_fb_probe
Modules linked in:
[<c003fe0c>] (unwind_backtrace+0x0/0x12c) from [<c00adccc>] (warn_slowpath_common+0x4c/0x64)
[<c00adccc>] (warn_slowpath_common+0x4c/0x64) from [<c00add64>] (warn_slowpath_fmt+0x2c/0x3c)
[<c00add64>] (warn_slowpath_fmt+0x2c/0x3c) from [<c0223c44>] (msm_fb_probe+0xf4/0xcbc)
[<c0223c44>] (msm_fb_probe+0xf4/0xcbc) from [<c026e624>] (platform_drv_probe+0x18/0x1c)
[<c026e624>] (platform_drv_probe+0x18/0x1c) from [<c026d354>] (driver_probe_device+0x144/0x264)
[<c026d354>] (driver_probe_device+0x144/0x264) from [<c026c78c>] (bus_for_each_drv+0x48/0x84)
[<c026c78c>] (bus_for_each_drv+0x48/0x84) from [<c026d5d0>] (device_attach+0x74/0xa0)
[<c026d5d0>] (device_attach+0x74/0xa0) from [<c026c5a4>] (bus_probe_device+0x24/0x40)
[<c026c5a4>] (bus_probe_device+0x24/0x40) from [<c026b4c4>] (device_add+0x3f0/0x570)
[<c026b4c4>] (device_add+0x3f0/0x570) from [<c026ec54>] (platform_device_add+0x13c/0x1a0)
[<c026ec54>] (platform_device_add+0x13c/0x1a0) from [<c02264b4>] (mdp_probe+0x828/0x940)
[<c02264b4>] (mdp_probe+0x828/0x940) from [<c026e624>] (platform_drv_probe+0x18/0x1c)
[<c026e624>] (platform_drv_probe+0x18/0x1c) from [<c026d354>] (driver_probe_device+0x144/0x264)
[<c026d354>] (driver_probe_device+0x144/0x264) from [<c026c78c>] (bus_for_each_drv+0x48/0x84)
[<c026c78c>] (bus_for_each_drv+0x48/0x84) from [<c026d5d0>] (device_attach+0x74/0xa0)
[<c026d5d0>] (device_attach+0x74/0xa0) from [<c026c5a4>] (bus_probe_device+0x24/0x40)
[<c026c5a4>] (bus_probe_device+0x24/0x40) from [<c026b4c4>] (device_add+0x3f0/0x570)
[<c026b4c4>] (device_add+0x3f0/0x570) from [<c026ec54>] (platform_device_add+0x13c/0x1a0)
[<c026ec54>] (platform_device_add+0x13c/0x1a0) from [<c023db98>] (mipi_dsi_probe+0x514/0x5d0)
[<c023db98>] (mipi_dsi_probe+0x514/0x5d0) from [<c026e624>] (platform_drv_probe+0x18/0x1c)
[<c026e624>] (platform_drv_probe+0x18/0x1c) from [<c026d354>] (driver_probe_device+0x144/0x264)
[<c026d354>] (driver_probe_device+0x144/0x264) from [<c026c78c>] (bus_for_each_drv+0x48/0x84)
[<c026c78c>] (bus_for_each_drv+0x48/0x84) from [<c026d5d0>] (device_attach+0x74/0xa0)
[<c026d5d0>] (device_attach+0x74/0xa0) from [<c026c5a4>] (bus_probe_device+0x24/0x40)
[<c026c5a4>] (bus_probe_device+0x24/0x40) from [<c026b4c4>] (device_add+0x3f0/0x570)
[<c026b4c4>] (device_add+0x3f0/0x570) from [<c026ec54>] (platform_device_add+0x13c/0x1a0)
[<c026ec54>] (platform_device_add+0x13c/0x1a0) from [<c02223b8>] (msm_fb_add_device+0x150/0x1b4)
[<c02223b8>] (msm_fb_add_device+0x150/0x1b4) from [<c051e830>] (mipi_himax_lcd_probe+0x38/0x108)
[<c051e830>] (mipi_himax_lcd_probe+0x38/0x108) from [<c026e624>] (platform_drv_probe+0x18/0x1c)
[<c026e624>] (platform_drv_probe+0x18/0x1c) from [<c026d354>] (driver_probe_device+0x144/0x264)
[<c026d354>] (driver_probe_device+0x144/0x264) from [<c026c78c>] (bus_for_each_drv+0x48/0x84)
[<c026c78c>] (bus_for_each_drv+0x48/0x84) from [<c026d5d0>] (device_attach+0x74/0xa0)
[<c026d5d0>] (device_attach+0x74/0xa0) from [<c026c5a4>] (bus_probe_device+0x24/0x40)
[<c026c5a4>] (bus_probe_device+0x24/0x40) from [<c026b4c4>] (device_add+0x3f0/0x570)
[<c026b4c4>] (device_add+0x3f0/0x570) from [<c026ec54>] (platform_device_add+0x13c/0x1a0)
[<c026ec54>] (platform_device_add+0x13c/0x1a0) from [<c02409ec>] (mipi_himax_device_register+0x7c/0xc0)
[<c02409ec>] (mipi_himax_device_register+0x7c/0xc0) from [<c001ac34>] (mipi_cmd_himax_hvga_pt_init+0x148/0x180)
[<c001ac34>] (mipi_cmd_himax_hvga_pt_init+0x148/0x180) from [<c0034388>] (do_one_initcall+0x94/0x164)
[<c0034388>] (do_one_initcall+0x94/0x164) from [<c00083d8>] (kernel_init+0x98/0x144)
[<c00083d8>] (kernel_init+0x98/0x144) from [<c003b0d0>] (kernel_thread_exit+0x0/0x8)
---[ end trace 65f8ea860415c051 ]---
下面考察设备probe链。
311static int __devinit mipi_samsung_lcd_probe(struct platform_device *pdev)
312{
…..
338 current_pdev = msm_fb_add_device(pdev);
339
340 if (current_pdev) {
341 mfd = platform_get_drvdata(current_pdev);
342 if (!mfd)
343 return -ENODEV;
344 if (mfd->key != MFD_KEY)
345 return -EINVAL;
346
347 mipi = &mfd->panel_info.mipi;
348
349 if (phy_settings != NULL)
350 mipi->dsi_phy_db = phy_settings;
351
352 if (dlane_swap)
353 mipi->dlane_swap = dlane_swap;
354 }
355 return 0;
356}
msm_fb_add_device做如下事情：
调用struct platform_device *msm_fb_device_alloc(struct msm_fb_panel_data *pdata, u32 type, u32 id)函数分配platform_device “mipi-dsi.type_devid”并设置其platform_data为msm_fb_panel_data。
以额外msm_fb_data_type结构分配framebuffer。
注册”mipi-dsi”设备platform_device_add(this_dev)。
“mipi-dsi”设备和驱动进行attach, match后，“mipi-dsi” driver的probe被调用到。
static int mipi_dsi_probe(struct platform_device *pdev) @ kernel/drivers/video/msm/mipi_dsi.c做如下事情(这次的设备ID是真正实例的了，不是1了)：
分配”mdp”设备实例并设置其数据，设置”mipi-dsi”设备操作函数，用于向下操作一级一级设备；
继续设置linux framebuffer的参数；
根据屏分辨率设置mipi-dsi工作频率；
注册该”mdp”设备实例；
“mdp”设备和驱动进行attach, match后，“mdp” driver的probe被调用到。
static int mdp_probe(struct platform_device *pdev) @ kernel/drivers/video/msm/mdp.c
分配”msm_fb”实例并设置其数据；
配置”mdp”工作模式；
注册”msm_fb”实例；
“msm_fb”设备和驱动进行attach, match后，“msm_fb” driver的probe被调用到。
static int msm_fb_probe(struct platform_device *pdev) @ kernel/drivers/video/msm/msm_fb.c
调用msm_fb_register设置linux framebuffer并register_framebuffer。
至此，系统中相关设备如下：
dsi_cmd_chimei_fwvga.0
dsi_cmd_samsung_fwvga.0
dsi_cmd_samsung_fwvga.1281 ->mipi_dsi.591105 -> mdp.591105 -> msm_fb.591105 -> fbx
dtv.0
dtv.458753 ->mdp.458753 -> msm_fb.458753 -> fbx
hdmi_msm.0
hdmi_msm.1 ->mdp.655361 -> msm_fb.655361 -> fbx (hdmi)
mdp.0
mipi_dsi.1
mipi_toshiba.0
msm_fb.0
Framebuffer设备注册后，使用FBIOCPUT_VSCREEN或FBIOCPAN_DISPLAY，驱动都会使用msmfb_pan_display进行响应显示，由于涉及到MDP，另文分析。
[END]