[ARM] S3C: ADC: Expose number of remaining conversions to

convert callback

This patch allow us to efficiently modify the number of
remaining conversions from the client side. This us useful
when we do not know in advance how many conversions we will
need or when we need to cancel pending conversions.

This change is simple enough to be compatible with existing
code that can just define the new pointer in the callback
and ignore it.

Sample usage:

http://tinyurl.com/s3c2410-ts-c (function stylus_adc_action).
Signed-off-by: NNelson Castillo <arhuaco@freaks-unidos.net>
Signed-off-by: NBen Dooks <ben-linux@fluff.org>

arch/arm/plat-s3c/include/plat/adc.h

@@ -22,7 +22,8 @@ extern int s3c_adc_start(struct s3c_adc_client *client,
 extern struct s3c_adc_client *
 	s3c_adc_register(struct platform_device *pdev,
 			 void (*select)(unsigned selected),
-			 void (*conv)(unsigned d0, unsigned d1),
+			 void (*conv)(unsigned d0, unsigned d1,
+				      unsigned *samples_left),
 			 unsigned int is_ts);
 
 extern void s3c_adc_release(struct s3c_adc_client *client);

arch/arm/plat-s3c24xx/adc.c

@@ -45,7 +45,8 @@ struct s3c_adc_client {
 	unsigned char		 channel;
 
 	void	(*select_cb)(unsigned selected);
-	void	(*convert_cb)(unsigned val1, unsigned val2);
+	void	(*convert_cb)(unsigned val1, unsigned val2,
+			      unsigned *samples_left);
 };
 
 struct adc_device {
@@ -158,7 +159,8 @@ static void s3c_adc_default_select(unsigned select)
 
 struct s3c_adc_client *s3c_adc_register(struct platform_device *pdev,
 					void (*select)(unsigned int selected),
-					void (*conv)(unsigned d0, unsigned d1),
+					void (*conv)(unsigned d0, unsigned d1,
+						     unsigned *samples_left),
 					unsigned int is_ts)
 {
 	struct s3c_adc_client *client;
@@ -227,9 +229,10 @@ static irqreturn_t s3c_adc_irq(int irq, void *pw)
 	data1 = readl(adc->regs + S3C2410_ADCDAT1);
 	adc_dbg(adc, "read %d: 0x%04x, 0x%04x\n", client->nr_samples, data0, data1);
 
-	(client->convert_cb)(data0 & 0x3ff, data1 & 0x3ff);
+	client->nr_samples--;
+	(client->convert_cb)(data0 & 0x3ff, data1 & 0x3ff, &client->nr_samples);
 
-	if (--client->nr_samples > 0) {
+	if (client->nr_samples > 0) {
 		/* fire another conversion for this */
 
 		client->select_cb(1);