soc-camera: add a free_bus method to struct soc_camera_link

From: Guennadi Liakhovetski <g.liakhovetski@gmx.de>

Currently pcm990 camera bus-width management functions request a GPIO and never
free it again. With this approach the GPIO extender driver cannot be unloaded
once camera drivers have been loaded, also unloading theb i2c-pxa bus driver
produces errors, because the GPIO extender driver cannot unregister properly.
Another problem is, that if camera drivers are once loaded before the GPIO
extender driver, the platform code marks the GPIO unavailable and only a reboot
helps to recover. Adding an explicit free_bus method and using it in mt9m001
and mt9v022 drivers fixes these problems.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Eric Miao <eric.miao@marvell.com>
---
 arch/arm/mach-pxa/pcm990-baseboard.c |   23 ++++++++++++++++-------
 drivers/media/video/mt9m001.c        |    3 +++
 drivers/media/video/mt9v022.c        |    3 +++
 include/media/soc_camera.h           |    1 +
 4 files changed, 23 insertions(+), 7 deletions(-)

1 files changed, 16 insertions, 7 deletions

diff --git a/linux/arch/arm/mach-pxa/pcm990-baseboard.c b/linux/arch/arm/mach-pxa/pcm990-baseboard.c
index 6c12b5a31..9ce1ef2e5 100644
--- a/linux/arch/arm/mach-pxa/pcm990-baseboard.c
+++ b/linux/arch/arm/mach-pxa/pcm990-baseboard.c
@@ -380,12 +380,12 @@ static struct pca953x_platform_data pca9536_data = {
 	.gpio_base	= NR_BUILTIN_GPIO,
 };
 
-static int gpio_bus_switch;
+static int gpio_bus_switch = -EINVAL;
 
 static int pcm990_camera_set_bus_param(struct soc_camera_link *link,
-		unsigned long flags)
+				       unsigned long flags)
 {
-	if (gpio_bus_switch <= 0) {
+	if (gpio_bus_switch < 0) {
 		if (flags == SOCAM_DATAWIDTH_10)
 			return 0;
 		else
@@ -404,25 +404,34 @@ static unsigned long pcm990_camera_query_bus_param(struct soc_camera_link *link)
 {
 	int ret;
 
-	if (!gpio_bus_switch) {
+	if (gpio_bus_switch < 0) {
 		ret = gpio_request(NR_BUILTIN_GPIO, "camera");
 		if (!ret) {
 			gpio_bus_switch = NR_BUILTIN_GPIO;
 			gpio_direction_output(gpio_bus_switch, 0);
-		} else
-			gpio_bus_switch = -EINVAL;
+		}
 	}
 
-	if (gpio_bus_switch > 0)
+	if (gpio_bus_switch >= 0)
 		return SOCAM_DATAWIDTH_8 | SOCAM_DATAWIDTH_10;
 	else
 		return SOCAM_DATAWIDTH_10;
 }
 
+static void pcm990_camera_free_bus(struct soc_camera_link *link)
+{
+	if (gpio_bus_switch < 0)
+		return;
+
+	gpio_free(gpio_bus_switch);
+	gpio_bus_switch = -EINVAL;
+}
+
 static struct soc_camera_link iclink = {
 	.bus_id	= 0, /* Must match with the camera ID above */
 	.query_bus_param = pcm990_camera_query_bus_param,
 	.set_bus_param = pcm990_camera_set_bus_param,
+	.free_bus = pcm990_camera_free_bus,
 };
 
 /* Board I2C devices. */