Re: [PATCH 2/3] ARM: cfa10036: Retrieve the board variant from the AT24

[Sascha Hauer <s.hauer@pengutronix.de>]

On Wed, Dec 12, 2012 at 03:10:55PM +0100, Maxime Ripard wrote:
> The AT24 found on the expansion boards store the variant of the board it
> is soldered onto.
> 
> That means that we are that way able to determine what expansion board
> is currently plugged in if any. If we can't communicate with the EEPROM,
> we just assume that only the CFA-10036 is there.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> ---
>  arch/arm/boards/crystalfontz-cfa10036/Makefile   |    2 +-
>  arch/arm/boards/crystalfontz-cfa10036/cfa10036.c |    4 +
>  arch/arm/boards/crystalfontz-cfa10036/hwdetect.c |   97 ++++++++++++++++++++++
>  arch/arm/boards/crystalfontz-cfa10036/hwdetect.h |   22 +++++
>  4 files changed, 124 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm/boards/crystalfontz-cfa10036/hwdetect.c
>  create mode 100644 arch/arm/boards/crystalfontz-cfa10036/hwdetect.h
> 
> diff --git a/arch/arm/boards/crystalfontz-cfa10036/Makefile b/arch/arm/boards/crystalfontz-cfa10036/Makefile
> index 75f0020..7e8d5e2 100644
> --- a/arch/arm/boards/crystalfontz-cfa10036/Makefile
> +++ b/arch/arm/boards/crystalfontz-cfa10036/Makefile
> @@ -1 +1 @@
> -obj-y += cfa10036.o
> +obj-y += cfa10036.o hwdetect.o
> diff --git a/arch/arm/boards/crystalfontz-cfa10036/cfa10036.c b/arch/arm/boards/crystalfontz-cfa10036/cfa10036.c
> index df0ead9..b59dbab 100644
> --- a/arch/arm/boards/crystalfontz-cfa10036/cfa10036.c
> +++ b/arch/arm/boards/crystalfontz-cfa10036/cfa10036.c
> @@ -42,6 +42,8 @@
>  
>  #include <generated/mach-types.h>
>  
> +#include "hwdetect.h"
> +
>  /* setup the CPU card internal signals */
>  static const uint32_t cfa10036_pads[] = {
>  	/* duart */
> @@ -120,6 +122,8 @@ static int cfa10036_devices_init(void)
>  	i2c_register_board_info(0, cfa10036_i2c_devices, ARRAY_SIZE(cfa10036_i2c_devices));
>  	add_generic_device_res("i2c-gpio", 0, NULL, 0, &i2c_gpio_pdata);
>  
> +	cfa10036_detect_hw();
> +
>  	return 0;
>  }
>  device_initcall(cfa10036_devices_init);
> diff --git a/arch/arm/boards/crystalfontz-cfa10036/hwdetect.c b/arch/arm/boards/crystalfontz-cfa10036/hwdetect.c
> new file mode 100644
> index 0000000..535a75f
> --- /dev/null
> +++ b/arch/arm/boards/crystalfontz-cfa10036/hwdetect.c
> @@ -0,0 +1,97 @@
> +/*
> + * Copyright (C) 2012 Free Electrons
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of
> + * the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + *
> + */
> +
> +#include <common.h>
> +
> +#include <environment.h>
> +#include <fcntl.h>
> +#include <fs.h>
> +#include <libbb.h>
> +
> +#include <asm/armlinux.h>
> +
> +enum board_type {
> +	BOARD_ID_CFA10036 = 0,
> +	BOARD_ID_CFA10037 = 1,
> +	BOARD_ID_CFA10049 = 2,
> +};
> +
> +struct cfa_eeprom_info {
> +	u8 board_id;
> +}__attribute__ ((packed));
> +
> +static int cfa10036_read_eeprom(const char *file, struct cfa_eeprom_info *info)
> +{
> +	int fd;
> +	int ret;
> +
> +	fd = open(file, O_RDONLY);
> +	if (fd < 0) {
> +		ret = fd;
> +		goto err;
> +	}
> +
> +	ret = read_full(fd, info, sizeof(*info));
> +	if (ret < 0)
> +		goto err_open;
> +
> +	if (ret < sizeof(*info)) {
> +		ret =  -EINVAL;
> +		goto err_open;
> +	}

This will never happen. read_full makes that sure.

> +
> +	ret = 0;
> +
> +err_open:
> +	close(fd);
> +err:
> +	if (ret)
> +		pr_err("can not read eeprom %s (%s)\n", file, strerror(ret));
> +	return ret;
> +}
> +
> +void cfa10036_detect_hw(void)
> +{
> +	enum board_type cfa_type;
> +	struct cfa_eeprom_info info;
> +	char *board_name;
> +	int ret;
> +
> +	ret = cfa10036_read_eeprom("/dev/eeprom0", &info);
> +	if (ret)
> +		cfa_type = BOARD_ID_CFA10036;
> +	else
> +		cfa_type = info.board_id;
> +
> +	switch (cfa_type) {
> +	case BOARD_ID_CFA10036:
> +		board_name = "cfa10036";
> +		break;
> +	case BOARD_ID_CFA10037:
> +		board_name = "cfa10037";
> +		break;
> +	case BOARD_ID_CFA10049:
> +		board_name = "cfa10049";
> +		break;
> +	default:
> +		pr_err("Board ID not supported\n");
> +		return;
> +	}
> +
> +	setenv("cfa_variant", board_name);
> +	export("cfa_variant");

I rather suggest:

	globalvar_add_simple("board.variant");
	setenv("global.board.variant", board_name);

(the name is debatable)

This way makes sure that the variable is available in every context
and shows up in 'devinfo global' which I think is a good place to
collect this kind of global information.

Additionally a:

BAREBOX_MAGICVAR_NAMED(global_board_variant, global.board.variant, "The board variant")

gives you the chance to describe the meaning of this variable.

Sascha


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