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

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Date:	Mon, 06 Dec 2010 11:03:13 -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 11:01 AM, Dirk Brandewie wrote:
> 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.
>
Obviously I meant .38 :-)

>> 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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>

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