linux-kernel - [PATCH v2 1/2] fb_ddc: Allow I2C adapters without SCL read capability

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Date:	Fri, 25 Sep 2015 00:14:13 +0200
From:	Ondrej Zary <linux@...nbow-software.org>
To:	Krzysztof Helt <krzysztof.h1@...pl>
Cc:	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 1/2] fb_ddc: Allow I2C adapters without SCL read capability

i2c-algo-bit allows I2C adapters without SCL read capability to work
but fb_ddc_read fails to work on them.

Fix fb_ddc_read to work with I2C adapters not capable of reading SCL.

Signed-off-by: Ondrej Zary <linux@...nbow-software.org>
---
 drivers/video/fbdev/core/fb_ddc.c |   28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/video/fbdev/core/fb_ddc.c b/drivers/video/fbdev/core/fb_ddc.c
index 94322cc..8bf5f2f 100644
--- a/drivers/video/fbdev/core/fb_ddc.c
+++ b/drivers/video/fbdev/core/fb_ddc.c
@@ -67,13 +67,17 @@ unsigned char *fb_ddc_read(struct i2c_adapter *adapter)
 		msleep(13);
 
 		algo_data->setscl(algo_data->data, 1);
-		for (j = 0; j < 5; j++) {
-			msleep(10);
-			if (algo_data->getscl(algo_data->data))
-				break;
+		if (algo_data->getscl) {
+			for (j = 0; j < 5; j++) {
+				msleep(10);
+				if (algo_data->getscl(algo_data->data))
+					break;
+			}
+			if (j == 5)
+				continue;
+		} else {
+			udelay(algo_data->udelay);
 		}
-		if (j == 5)
-			continue;
 
 		algo_data->setsda(algo_data->data, 0);
 		msleep(15);
@@ -89,10 +93,14 @@ unsigned char *fb_ddc_read(struct i2c_adapter *adapter)
 		msleep(15);
 
 		algo_data->setscl(algo_data->data, 1);
-		for (j = 0; j < 10; j++) {
-			msleep(10);
-			if (algo_data->getscl(algo_data->data))
-				break;
+		if (algo_data->getscl) {
+			for (j = 0; j < 10; j++) {
+				msleep(10);
+				if (algo_data->getscl(algo_data->data))
+					break;
+			}
+		} else {
+			udelay(algo_data->udelay);
 		}
 
 		algo_data->setsda(algo_data->data, 1);
-- 
Ondrej Zary

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