Hi Sascha,

On Mon, 2015-03-23 at 08:39 +0100, Sascha Hauer wrote:

On Sat, Mar 21, 2015 at 02:05:22PM +0800, Eddie Huang wrote:

quoted

Add mediatek MT8173 I2C controller driver. Compare to I2C controller
of earlier mediatek SoC, MT8173 fix write-then-read limitation, and
also increase message size to 64kb.

[...]

quoted

+static const struct i2c_adapter_quirks mt8173_i2c_quirks = {
+	.max_num_msgs = MAX_MSG_NUM_MT8173,
+	.max_write_len = MAX_DMA_TRANS_SIZE_MT8173,
+	.max_read_len = MAX_DMA_TRANS_SIZE_MT8173,
+	.max_comb_1st_msg_len = MAX_DMA_TRANS_SIZE_MT8173,
+	.max_comb_2nd_msg_len = MAX_WRRD_TRANS_SIZE_MT8173,
+};
+
 static int mtk_i2c_probe(struct platform_device *pdev)
 {
 	int ret = 0;

@@ -587,7 +626,8 @@ static int mtk_i2c_probe(struct platform_device *pdev)
 		return -EINVAL;
 
 	i2c->platform_compat = mtk_get_device_prop(pdev);
-	if (i2c->have_pmic && (i2c->platform_compat & COMPAT_MT6577))
+	if (i2c->have_pmic && (i2c->platform_compat &
+			(COMPAT_MT6577 | COMPAT_MT8173)))
 		return -EINVAL;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

@@ -613,7 +653,10 @@ static int mtk_i2c_probe(struct platform_device *pdev)
 	i2c->adap.dev.parent = &pdev->dev;
 	i2c->adap.owner = THIS_MODULE;
 	i2c->adap.algo = &mtk_i2c_algorithm;
-	i2c->adap.quirks = &mt6577_i2c_quirks;
+	if (i2c->platform_compat & COMPAT_MT8173)
+		i2c->adap.quirks = &mt8173_i2c_quirks;
+	else
+		i2c->adap.quirks = &mt6577_i2c_quirks;

Instead of putting an integer into struct of_device_id you should
introduce a

struct mtk_i2c_data {
	struct i2c_adapter_quirks quirks;
	int compat;
	/* Additional SoC specific data */
};

and put a pointer to this directly into the of_device_id. This way you
need less casting and can put newly discovered differences diretly into
some data struct and don't have to introduce if(socxy) ... else ...
everytime.

Thanks your suggestion. I will use capability struct like 

struct mtk_i2c_compatible {
	unsigned char pmic_i2c;
	unsigned char dcm;
	unsigned char auto_restart;
	const struct i2c_adapter_quirks *quirks;
};

And pass in of_device_id, then remove all if(socxy).... else ... in
driver.

Eddie