Re: [PATCH] regmap: Add Kconfig option for debugfs register writes

David Rientjes
2014-06-17T19:56:58Z

On Tue, 17 Jun 2014, Markus Pargmann wrote:

> To enable writing of registers through the regmap debugfs interface, it
> was necessary to alter the regmap-debugfs.c source code. This is not
> really practical.
>
> As this is a powerful tool for debugging, this patch creates an expert
> kconfig option for this function. This makes it easier to enable
> register writing in the kernel.
>
> This patch also fixes the file mode when the regmap debugfs write code is
> compiled.
>

Forcing users to enable CONFIG_EXPERT for this doesn't seem appropriate,
it enables things by default and has really become a separate config of
its own. You might want to consider removing this dependency unless you
have a strong reason for keeping it.

> Cc: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> ---
> drivers/base/regmap/Kconfig | 14 ++++++++++++++
> drivers/base/regmap/regmap-debugfs.c | 16 ++++++++++------
> 2 files changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/base/regmap/Kconfig b/drivers/base/regmap/Kconfig
> index 4251570610c9..ce86600dbe75 100644
> --- a/drivers/base/regmap/Kconfig
> +++ b/drivers/base/regmap/Kconfig
> @@ -23,3 +23,17 @@ config REGMAP_MMIO
>
> config REGMAP_IRQ
> bool
> +
> +config REGMAP_ALLOW_WRITE_DEBUGFS
> + default n
> + depends on DEBUG_FS
> + depends on EXPERT
> + depends on REGMAP
> + bool "Regmap, allow direct register writes through debugfs"
> + help
> + This option enables regmap debugfs write support. If this is enabled,
> + you can directly write registers using the registers file in the
> + regmap debugfs.
> +
> + This is potentially dangerous. Do not enable this option unless you
> + know what you are doing.
> diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
> index 45d812c0ea77..12906f2bdf00 100644
> --- a/drivers/base/regmap/regmap-debugfs.c
> +++ b/drivers/base/regmap/regmap-debugfs.c
> @@ -261,13 +261,10 @@ static ssize_t regmap_map_read_file(struct file *file, char __user *user_buf,
> count, ppos);
> }
>
> -#undef REGMAP_ALLOW_WRITE_DEBUGFS
> -#ifdef REGMAP_ALLOW_WRITE_DEBUGFS
> +#if IS_ENABLED(CONFIG_REGMAP_ALLOW_WRITE_DEBUGFS)
> /*
> * This can be dangerous especially when we have clients such as
> - * PMICs, therefore don't provide any real compile time configuration option
> - * for this feature, people who want to use this will need to modify
> - * the source code directly.
> + * PMICs, therefore this function can only be selected in expert kconfig mode.
> */
> static ssize_t regmap_map_write_file(struct file *file,
> const char __user *user_buf,
> @@ -512,7 +509,14 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
> map, &regmap_reg_ranges_fops);
>
> if (map->max_register || regmap_readable(map, 0)) {
> - debugfs_create_file("registers", 0400, map->debugfs,
> + unsigned int registers_mode;
> +
> + if (IS_ENABLED(CONFIG_REGMAP_ALLOW_WRITE_DEBUGFS))
> + registers_mode = 0600;
> + else
> + registers_mode = 0400;
> +
> + debugfs_create_file("registers", registers_mode, map->debugfs,
> map, &regmap_map_fops);
> debugfs_create_file("access", 0400, map->debugfs,
> map, &regmap_access_fops);