linux-kernel - Re: [PATCH] of/fdt: add kernel command line option for dtb

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Date:	Mon, 06 Dec 2010 11:01:54 -0800
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	Stephen Neuendorffer <stephen.neuendorffer@...inx.com>
CC:	linux-kernel@...r.kernel.org, Randy Dunlap <rdunlap@...otime.net>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH] of/fdt: add kernel command line option for dtb_compat
 string

On 12/06/2010 10:37 AM, Stephen Neuendorffer wrote:
>
>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index c1360e0..ca1318c 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -15,6 +15,8 @@
>>   #include<linux/of_fdt.h>
>>   #include<linux/string.h>
>>   #include<linux/errno.h>
>> +#include<asm-generic/vmlinux.lds.h>
>> +
>>
>>   #ifdef CONFIG_PPC
>>   #include<asm/machdep.h>
>> @@ -604,3 +606,49 @@ void __init unflatten_device_tree(void)
>>
>>   	pr_debug("<- unflatten_device_tree()\n");
>>   }
>> +
>> +extern uint8_t __dtb_start[];
>> +extern uint8_t __dtb_end[];
>> +static void __init *of_flat_dt_find_compatible_dtb(char *name)
>> +{
>> +	void *rc = NULL;
>> +	unsigned long root, size;
>> +	struct boot_param_header  *orig_initial_boot_params;
>> +	uint8_t *blob;
>> +
>> +	orig_initial_boot_params = initial_boot_params;
>> +	blob = __dtb_start;
>> +	initial_boot_params = (struct boot_param_header *)blob;
>
> Oy... can you avoid the pointer dance by using of_fdt_is_compatible()
> from my recent set of patches?

I would like to get rid of the pointer dance. Is your patch set going to make it 
into .37?  I didn't see any acks.

> It takes a blob argument.  Then the loop below goes away.
>

The loop will still be needed since multiple DTBs may be linked into the image. 
using your  of_fdt_is_compatible() will make the loop a lot more readable though.

--Dirk

> Steve
>
>> +
>> +
>> +	while (blob<  __dtb_end) {
>> +		if (be32_to_cpu(initial_boot_params->magic) !=
> OF_DT_HEADER) {
>> +			WARN(1, "Invalid device tree blob in
> vmlinux\n");
>> +			break;
>> +		}
>> +
>> +		root = of_get_flat_dt_root();
>> +		if (of_flat_dt_is_compatible(root, name)>  0) {
>> +			rc = blob;
>> +			break;
>> +		}
>> +
>> +		size =  be32_to_cpu(initial_boot_params->totalsize);
>> +		blob =  PTR_ALIGN(blob + size, STRUCT_ALIGNMENT);
>> +		initial_boot_params = (struct boot_param_header *)blob;
>> +	}
>> +
>> +	if (rc == NULL)
>> +		initial_boot_params = orig_initial_boot_params;
>> +	return rc;
>> +}
>> +
>> +
>> +static int __init of_flat_dtb_compat_setup(char *line)
>> +{
>> +	if (!initial_boot_params)
>> +		initial_boot_params =
> of_flat_dt_find_compatible_dtb(line);
>> +	return 1;
>> +}
>> +
>> +early_param("dtb_compat", of_flat_dtb_compat_setup);
>> +
>> --
>> 1.7.2.3
>>
>> _______________________________________________
>> devicetree-discuss mailing list
>> devicetree-discuss@...ts.ozlabs.org
>> https://lists.ozlabs.org/listinfo/devicetree-discuss
>
>
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