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Date: Thu, 21 Jun 2012 11:34:10 +0200
From: Florian Fainelli <florian@...nwrt.org>
To: Richard Genoud <richard.genoud@...il.com>
Cc: Russell King <linux@....linux.org.uk>,
Nicolas Pitre <nicolas.pitre@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: zImage: Allow DTB command line concatenation with ATAG_CMDLINE
Hello,
On Thursday 21 June 2012 10:56:57 Richard Genoud wrote:
> This patch allows the ATAG_CMDLINE provided by the bootloader to be
> concatenated to the bootargs property of the device tree.
>
> This is useful to merge static values defined in the device tree with the
> boot loader's (possibly) more dynamic values, such as startup reasons and
more.
>
> The bootloader should use the device tree to pass those values to the
kernel,
> but that's not always simple (old bootloader or very small one).
>
> The behaviour is the same as the one introduced by Victor Boivie in
> 4394c1244249198c6b85093d46935b761b36ae05 by extending the CONFIG_CMDLINE.
I had a similar need recently, and I was pointed at this more generic
solution: http://www.mail-archive.com/devicetree-
discuss@...ts.ozlabs.org/msg10448.html
The only thing which is ARM-specific and not yet resolved is the following: if
you have ARM_ATAG_DTB_COMPAT enabled, the kernel command-line contains only
the bootloader supplied command-line and not bootloader + bootargs from DT. I
have not yet had a chance to get this sorted.
>
> Signed-off-by: Richard Genoud <richard.genoud@...il.com>
> ---
> arch/arm/Kconfig | 19 +++++++++
> arch/arm/boot/compressed/atags_to_fdt.c | 62
++++++++++++++++++++++++++++++-
> 2 files changed, 79 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 84449dd..ff4b6e6 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1959,6 +1959,25 @@ config ARM_ATAG_DTB_COMPAT
> bootloaders, this option allows zImage to extract the information
> from the ATAG list and store it at run time into the appended DTB.
>
> +choice
> + prompt "Kernel command line type" if ARM_ATAG_DTB_COMPAT
> + default ARM_ATAG_DTB_COMPAT_CMDLINE_FROM_BOOTLOADER
> +
> +config ARM_ATAG_DTB_COMPAT_CMDLINE_FROM_BOOTLOADER
> + bool "Use bootloader kernel arguments if available"
> + help
> + Uses the command-line options passed by the boot loader instead of
> + the device tree bootargs property. If the boot loader doesn't provide
> + any, the device tree bootargs property will be used.
> +
> +config ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND
> + bool "Extend with bootloader kernel arguments"
> + help
> + The command-line arguments provided by the boot loader will be
> + appended to the the device tree bootargs property.
> +
> +endchoice
> +
> config CMDLINE
> string "Default kernel command string"
> default ""
> diff --git a/arch/arm/boot/compressed/atags_to_fdt.c
b/arch/arm/boot/compressed/atags_to_fdt.c
> index 797f04b..aabc02a 100644
> --- a/arch/arm/boot/compressed/atags_to_fdt.c
> +++ b/arch/arm/boot/compressed/atags_to_fdt.c
> @@ -1,6 +1,12 @@
> #include <asm/setup.h>
> #include <libfdt.h>
>
> +#if defined(CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND)
> +#define do_extend_cmdline 1
> +#else
> +#define do_extend_cmdline 0
> +#endif
> +
> static int node_offset(void *fdt, const char *node_path)
> {
> int offset = fdt_path_offset(fdt, node_path);
> @@ -36,6 +42,48 @@ static int setprop_cell(void *fdt, const char *node_path,
> return fdt_setprop_cell(fdt, offset, property, val);
> }
>
> +static const void *getprop(const void *fdt, const char *node_path,
> + const char *property, int *len)
> +{
> + int offset = fdt_path_offset(fdt, node_path);
> +
> + if (offset == -FDT_ERR_NOTFOUND)
> + return NULL;
> +
> + return fdt_getprop(fdt, offset, property, len);
> +}
> +
> +static void merge_fdt_bootargs(void *fdt, const char *fdt_cmdline)
> +{
> + char cmdline[COMMAND_LINE_SIZE];
> + const char *fdt_bootargs;
> + char *ptr = cmdline;
> + int len = 0;
> +
> + /* copy the fdt command line into the buffer */
> + fdt_bootargs = getprop(fdt, "/chosen", "bootargs", &len);
> + if (fdt_bootargs)
> + if (len < COMMAND_LINE_SIZE) {
> + memcpy(ptr, fdt_bootargs, len);
> + /* len is the length of the string
> + * including the NULL terminator */
> + ptr += len - 1;
> + }
> +
> + /* and append the ATAG_CMDLINE */
> + if (fdt_cmdline) {
> + len = strlen(fdt_cmdline);
> + if (ptr - cmdline + len + 2 < COMMAND_LINE_SIZE) {
> + *ptr++ = ' ';
> + memcpy(ptr, fdt_cmdline, len);
> + ptr += len;
> + }
> + }
> + *ptr = '\0';
> +
> + setprop_string(fdt, "/chosen", "bootargs", cmdline);
> +}
> +
> /*
> * Convert and fold provided ATAGs into the provided FDT.
> *
> @@ -72,8 +120,18 @@ int atags_to_fdt(void *atag_list, void *fdt, int
total_space)
>
> for_each_tag(atag, atag_list) {
> if (atag->hdr.tag == ATAG_CMDLINE) {
> - setprop_string(fdt, "/chosen", "bootargs",
> - atag->u.cmdline.cmdline);
> + /* Append the ATAGS command line to the device tree
> + * command line.
> + * NB: This means that if the same parameter is set in
> + * the device tree and in the tags, the one from the
> + * tags will be chosen.
> + */
> + if (do_extend_cmdline)
> + merge_fdt_bootargs(fdt,
> + atag->u.cmdline.cmdline);
> + else
> + setprop_string(fdt, "/chosen", "bootargs",
> + atag->u.cmdline.cmdline);
> } else if (atag->hdr.tag == ATAG_MEM) {
> if (memcount >= sizeof(mem_reg_property)/4)
> continue;
> --
> 1.7.2.5
>
> --
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