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

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Message-ID: <20101230213424.GC3220@angua.secretlab.ca>
Date:	Thu, 30 Dec 2010 14:34:24 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
Cc:	linux-kernel@...r.kernel.org, Randy Dunlap <rdunlap@...otime.net>,
	linux-doc@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org
Subject: Re: [PATCH] of/fdt: add kernel command line option for dtb_compat
 string

On Wed, Dec 22, 2010 at 12:04:56PM -0800, Dirk Brandewie wrote:
> On 12/06/2010 09:54 AM, dirk.brandewie@...il.com wrote:
> >From: Dirk Brandewie<dirk.brandewie@...il.com>
> >
> >Adds a kernel command line option "dtb_compat=<string>".  This string
> >will be used to select the first compatible device tree blob linked
> >into the kernel if a device tree blob is was *not* passed in by the
> >bootloader.
> >
> >Signed-off-by: Dirk Brandewie<dirk.brandewie@...il.com>
> >---
> >  Documentation/kernel-parameters.txt |    8 ++++++
> >  drivers/of/fdt.c                    |   48 +++++++++++++++++++++++++++++++++++
> >  2 files changed, 56 insertions(+), 0 deletions(-)
> >
> >diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> >index 92e83e5..64093e5 100644
> >--- a/Documentation/kernel-parameters.txt
> >+++ b/Documentation/kernel-parameters.txt
> >@@ -655,6 +655,14 @@ and is between 256 and 4096 characters. It is defined in the file
> >
> >  	dscc4.setup=	[NET]
> >
> >+	dtb_compat=	[KNL]
> >+			Specify the "compatible" string for the device
> >+			tree blob present in the vmlinux image.  This
> >+			string will be used to select the first device
> >+			tree blob whose compatible property matches
> >+			the string if a dtb was NOT passed in by the
> >+			bootloader.
> >+
> >  	dynamic_printk	Enables pr_debug()/dev_dbg() calls if
> >  			CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
> >  			These can also be switched on/off via
> >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;
> >+
> >+	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);
> >+
> Any more comments on this patch? Is it good to go or DOA?

Not DOA, but I want to discuss the linking vs. wrapper issue again
before I commit to merging it.  BTW, sorry for being MIA on this stuff
for pretty much all December.  I got over committed, but things should
be better now.

g.

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