Subject: Re: [PATCH 1/3] serial/imx: add device tree support

From: Mitch Bradley <[email-masked]>
Date: Tue, 21 Jun 2011 08:32:50 -1000

I wonder if it makes sense to create a new device node "/linux-devices" to express a desired mapping from device nodes to /dev entries?  The properties could be the names of device special files and the values the corresponding node phandles.

On 6/21/2011 3:55 AM, Shawn Guo wrote:
> Hi Grant,
> 
> I just gave a try to use aliases node for identify the device index.
> Please take a look and let me know if it's what you expect.
> 
> On Sun, Jun 19, 2011 at 03:30:02PM +0800, Shawn Guo wrote:
> [...]
>>>>
>>>> +#ifdef CONFIG_OF
>>>> +static int serial_imx_probe_dt(struct imx_port *sport,
>>>> +		struct platform_device *pdev)
>>>> +{
>>>> +	struct device_node *node = pdev->dev.of_node;
>>>> +	const __be32 *line;
>>>> +
>>>> +	if (!node)
>>>> +		return -ENODEV;
>>>> +
>>>> +	line = of_get_property(node, "id", NULL);
>>>> +	if (!line)
>>>> +		return -ENODEV;
>>>> +
>>>> +	sport->port.line = be32_to_cpup(line) - 1;
>>>
>>> Hmmm, I really would like to be rid of this.  Instead, if uarts must
>>> be enumerated, the driver should look for a /aliases/uart* property
>>> that matches the of_node.  Doing it that way is already established in
>>> the OpenFirmware documentation, and it ensures there are no overlaps
>>> in the global namespace.
>>>
>>
>> I just gave one more try to avoid using 'aliases', and you gave a
>> 'no' again.  Now, I know how hard you are on this.  Okay, I start
>> thinking about your suggestion seriously :)
>>
>>> We do need some infrastructure to make that easier though.  Would you
>>> have time to help put that together?
>>>
>> Ok, I will give it a try.
>>
> 
> diff --git a/arch/arm/boot/dts/imx51-babbage.dts b/arch/arm/boot/dts/imx51-babbage.dts
> index da0381a..f4a5c3c 100644
> --- a/arch/arm/boot/dts/imx51-babbage.dts
> +++ b/arch/arm/boot/dts/imx51-babbage.dts
> @@ -18,6 +18,12 @@
>   	compatible = "fsl,imx51-babbage", "fsl,imx51";
>   	interrupt-parent =<&tzic>;
> 
> +	aliases {
> +		serial0 =&uart0;
> +		serial1 =&uart1;
> +		serial2 =&uart2;
> +	};
> +
>   	chosen {
>   		bootargs = "console=ttymxc0,115200 root=/dev/mmcblk0p3 rootwait";
>   	};
> @@ -47,29 +53,29 @@
>   			reg =<0x70000000 0x40000>;
>   			ranges;
> 
> -			uart@7000c000 {
> +			uart2: uart@7000c000 {
>   				compatible = "fsl,imx51-uart", "fsl,imx21-uart";
>   				reg =<0x7000c000 0x4000>;
>   				interrupts =<33>;
>   				id =<3>;
> -				fsl,has-rts-cts;
> +				fsl,uart-has-rtscts;
>   			};
>   		};
> 
> -		uart@73fbc000 {
> +		uart0: uart@73fbc000 {
>   			compatible = "fsl,imx51-uart", "fsl,imx21-uart";
>   			reg =<0x73fbc000 0x4000>;
>   			interrupts =<31>;
>   			id =<1>;
> -			fsl,has-rts-cts;
> +			fsl,uart-has-rtscts;
>   		};
> 
> -		uart@73fc0000 {
> +		uart1: uart@73fc0000 {
>   			compatible = "fsl,imx51-uart", "fsl,imx21-uart";
>   			reg =<0x73fc0000 0x4000>;
>   			interrupts =<32>;
>   			id =<2>;
> -			fsl,has-rts-cts;
> +			fsl,uart-has-rtscts;
>   		};
>   	};
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 632ebae..13df5d2 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -737,6 +737,37 @@ err0:
>   EXPORT_SYMBOL(of_parse_phandles_with_args);
> 
>   /**
> + *	of_get_device_index - Get device index by looking up "aliases" node
> + *	@np:	Pointer to device node that asks for device index
> + *	@name:	The device alias without index number
> + *
> + *	Returns the device index if find it, else returns -ENODEV.
> + */
> +int of_get_device_index(struct device_node *np, const char *alias)
> +{
> +	struct device_node *aliases = of_find_node_by_name(NULL, "aliases");
> +	struct property *prop;
> +	char name[32];
> +	int index = 0;
> +
> +	if (!aliases)
> +		return -ENODEV;
> +
> +	while (1) {
> +		snprintf(name, sizeof(name), "%s%d", alias, index);
> +		prop = of_find_property(aliases, name, NULL);
> +		if (!prop)
> +			return -ENODEV;
> +		if (np == of_find_node_by_path(prop->value))
> +			break;
> +		index++;
> +	}
> +
> +	return index;
> +}
> +EXPORT_SYMBOL(of_get_device_index);
> +
> +/**
>    * prom_add_property - Add a property to a node
>    */
>   int prom_add_property(struct device_node *np, struct property *prop)
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index da436e0..852668f 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1271,18 +1271,18 @@ static int serial_imx_probe_dt(struct imx_port *sport,
>   	struct device_node *node = pdev->dev.of_node;
>   	const struct of_device_id *of_id =
>   			of_match_device(imx_uart_dt_ids,&pdev->dev);
> -	const __be32 *line;
> +	int line;
> 
>   	if (!node)
>   		return -ENODEV;
> 
> -	line = of_get_property(node, "id", NULL);
> -	if (!line)
> +	line = of_get_device_index(node, "serial");
> +	if (IS_ERR_VALUE(line))
>   		return -ENODEV;
> 
> -	sport->port.line = be32_to_cpup(line) - 1;
> +	sport->port.line = line;
> 
> -	if (of_get_property(node, "fsl,has-rts-cts", NULL))
> +	if (of_get_property(node, "fsl,uart-has-rtscts", NULL))
>   		sport->have_rtscts = 1;
> 
>   	if (of_get_property(node, "fsl,irda-mode", NULL))
> diff --git a/include/linux/of.h b/include/linux/of.h
> index bfc0ed1..3153752 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -213,6 +213,8 @@ extern int of_parse_phandles_with_args(struct device_node *np,
>   	const char *list_name, const char *cells_name, int index,
>   	struct device_node **out_node, const void **out_args);
> 
> +extern int of_get_device_index(struct device_node *np, const char *alias);
> +
>   extern int of_machine_is_compatible(const char *compat);
> 
>   extern int prom_add_property(struct device_node* np, struct property* prop);
>