Re: [Xen-devel] [PATCH V1 17/29] xen/arm: Mark each device used by Xen as disabled in DOM0 FDT

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 08/29/2013 02:19 AM, Bamvor Jian Zhang wrote:
> Hi Julien

Hi Bamvor,

>> On some board, there is no alias to the UART. To avoid modification in
>> the device tree, dt-uart should also search device by path.
>>
>> To distinguish an alias from a path, dt-uart will check the first character.
>> If it's a / then it's path, otherwise it's an alias.
>>
>> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
>> Acked-by: Ian Cambell <ian.campbell@xxxxxxxxxx>
>> ---
>>  xen/drivers/char/dt-uart.c |   16 ++++++++++------
>>  1 file changed, 10 insertions(+), 6 deletions(-)
>>
>> diff --git a/xen/drivers/char/dt-uart.c b/xen/drivers/char/dt-uart.c
>> index 93bb0f5..d7204fb 100644
>> --- a/xen/drivers/char/dt-uart.c
>> +++ b/xen/drivers/char/dt-uart.c
>> @@ -26,9 +26,10 @@
>>  
>>  /*
>>   * Configure UART port with a string:
>> - * alias,options
>> + * path,options
>>   *
>> - * @alias: alias used in the device tree for the UART
>> + * @path: full path used in the device tree for the UART. If the path
>> + * doesn't start with '/', we assuming that it's an alias.
>>   * @options: UART speficic options (see in each UART driver)
>>   */
>>  static char __initdata opt_dtuart[30] = "";
>> @@ -38,7 +39,7 @@ void __init dt_uart_init(void)
>>  {
>>      struct dt_device_node *dev;
>>      int ret;
>> -    const char *devalias = opt_dtuart;
>> +    const char *devpath = opt_dtuart;
>>      char *options;
>>  
>>      if ( !console_has("dtuart") || !strcmp(opt_dtuart, "") )
>> @@ -53,12 +54,15 @@ void __init dt_uart_init(void)
>>      else
>>          options = "";
>>  
>> -    early_printk("Looking for UART console %s\n", devalias);
>> -    dev = dt_find_node_by_alias(devalias);
>> +    early_printk("Looking for UART console %s\n", devpath);
>> +    if ( *devpath == '/' )
>> +        dev = dt_find_node_by_path(devpath);
>> +    else
>> +        dev = dt_find_node_by_alias(devpath);
> if '/' start an alias, it should be

From the ePAR
(http://www.power.org/resources/downloads/Power_ePAPR_APPROVED_v1.0.pdf)
section 3.3: an alias name must match the following pattern: [0-9a-z-]+
So we can't find '/' in the alias.

> +    if ( *devpath == '/' )
> +        dev = dt_find_node_by_alias(devpath);
> +    else
> +        dev = dt_find_node_by_path(devpath);

A path always start by '/'. With your solution, it won't be possible to
get the UART by path.

-- 
Julien Grall

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