V4L/DVB (6952): Add code for autoloading em28xx-alsa, if needed

Older em28xx devices does implement standard Audio Class.

However, on newer devices, this were replaced by a Vendor Class. This
patch autodetects that an em28xx lacks Audio Class and auto-loads
em28xx-alsa, for the devices that implements only a Vendor Class.

For devices with Audio Class, snd-usb-audio module will provide an ALSA
interface.

This patch uses the request_module_async function as defined on cx88-mpeg.c, 
originally wrote by Markus Rechberger.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

3 files changed, 41 insertions, 1 deletions

diff --git a/drivers/media/video/em28xx/em28xx-audio.c b/drivers/media/video/em28xx/em28xx-audio.c
index c91ff52aefa..941357c4f3f 100644
--- a/drivers/media/video/em28xx/em28xx-audio.c
+++ b/drivers/media/video/em28xx/em28xx-audio.c
@@ -472,7 +472,6 @@ static struct em28xx_ops audio_ops = {
 
 static int __init em28xx_alsa_register(void)
 {
-        request_module("em28xx");
         return em28xx_register_extension(&audio_ops);
 }
 
diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index caa4757b7eb..a03e9d724b5 100644
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -1668,6 +1668,10 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
         dev->em28xx_read_reg_req = em28xx_read_reg_req;
         dev->is_em2800 = em28xx_boards[dev->model].is_em2800;
 
+        errCode = em28xx_read_reg(dev, CHIPID_REG);
+        if (errCode >= 0)
+                em28xx_info("em28xx chip ID = %d\n", errCode);
+
         em28xx_pre_card_setup(dev);
 
         errCode = em28xx_config(dev);
@@ -1794,6 +1798,25 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
         return 0;
 }
 
+#if defined(CONFIG_MODULES) && defined(MODULE)
+static void request_module_async(struct work_struct *work)
+{
+        struct em28xx *dev = container_of(work,
+                             struct em28xx, request_module_wk);
+
+        if (!dev->has_audio_class)
+                request_module("em28xx-alsa");
+}
+
+static void request_modules(struct em28xx *dev)
+{
+        INIT_WORK(&dev->request_module_wk, request_module_async);
+        schedule_work(&dev->request_module_wk);
+}
+#else
+#define request_modules(dev)
+#endif /* CONFIG_MODULES */
+
 /*
  * em28xx_usb_probe()
  * checks for supported devices
@@ -1864,6 +1887,18 @@ static int em28xx_usb_probe(struct usb_interface *interface,
         dev->devno = nr;
         dev->model = id->driver_info;
 
+        /* Checks if audio is provided by some interface */
+        for (i = 0; i < udev->config->desc.bNumInterfaces; i++) {
+                uif = udev->config->interface[i];
+                if (uif->altsetting[0].desc.bInterfaceClass == USB_CLASS_AUDIO) {
+                        dev->has_audio_class = 1;
+                        break;
+                }
+        }
+
+        printk(KERN_INFO DRIVER_NAME " %s usb audio class\n",
+                   dev->has_audio_class ? "Has" : "Doesn't have");
+
         /* compute alternate max packet sizes */
         uif = udev->actconfig->interface[0];
 
@@ -1900,6 +1935,9 @@ static int em28xx_usb_probe(struct usb_interface *interface,
 
         /* save our data pointer in this interface device */
         usb_set_intfdata(interface, dev);
+
+        request_modules(dev);
+
         return 0;
 }
 
diff --git a/drivers/media/video/em28xx/em28xx.h b/drivers/media/video/em28xx/em28xx.h
index c2d9ae0ac61..9eb213132da 100644
--- a/drivers/media/video/em28xx/em28xx.h
+++ b/drivers/media/video/em28xx/em28xx.h
@@ -246,6 +246,7 @@ struct em28xx {
         unsigned int has_msp34xx:1;
         unsigned int has_tda9887:1;
         unsigned int stream_on:1;       /* Locks streams */
+        unsigned int has_audio_class:1;
 
         int video_inputs;       /* number of video inputs */
         struct list_head        devlist;
@@ -295,6 +296,8 @@ struct em28xx {
         enum em28xx_stream_state stream;
         enum em28xx_io_method io;
 
+        struct work_struct         request_module_wk;
+
         /* locks */
         struct mutex lock;
         spinlock_t queue_lock;