Re: [PATCH] mtd: add mtdram device (which build mtd over ram area - useful for FRAM oder MRAM)

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

Hi Sebastian,

On Thu, Aug 28, 2014 at 10:59:51AM +0200, basti@linux-source.de wrote:
> This adds support for MTD in RAM devices (like FRAM or MRAM).
> 
> Signed-off-by: Sebastian Block <basti@linux-source.de>
> 
> ---
>  drivers/mtd/devices/Kconfig  |    6 ++
>  drivers/mtd/devices/Makefile |    1 +
>  drivers/mtd/devices/mtdram.c |  132
> ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 139 insertions(+)
>  create mode 100644 drivers/mtd/devices/mtdram.c
> 
> diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig
> index 94668a2..c512242 100644
> --- a/drivers/mtd/devices/Kconfig
> +++ b/drivers/mtd/devices/Kconfig
> @@ -64,4 +64,10 @@ config MTD_DOCG3
>           M-Systems and now Sandisk. The support is very experimental,
>           and doesn't give access to any write operations.
> 
> +config MTD_MTDRAM
> +       tristate "Provide test driver using RAM"

This description is probably directly takes from the Kernel. I think
something like "driver for memory mapped MRAM/FRAM" would be more
appropriate.

> new file mode 100644
> index 0000000..bd0bbb4
> --- /dev/null
> +++ b/drivers/mtd/devices/mtdram.c
> @@ -0,0 +1,132 @@
> +/*
> + * MTD RAM driver - a mtd test device driver
> + *
> + * Author: Sebastian Block <basti@linux-source.de>
> + * Copyright (c) 2014
> + *
> + * Some parts are based on mtdram.c found in Linux kernel
> + * by   Alexander Larsson <alex@cendio.se>
> + * and  Joern Engel <joern@wh.fh-wedel.de>.
> + *
> + * This code is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +#include <common.h>
> +#include <environment.h>
> +#include <errno.h>
> +#include <init.h>
> +#include <io.h>
> +#include <linux/mtd/mtd.h>
> +#include <malloc.h>
> +#include <of.h>
> +
> +struct mtdram_priv_data {
> +       struct mtd_info mtd;
> +       void *base;
> +};
> +
> +static int ram_erase(struct mtd_info *mtd, struct erase_info *instr) {

The coding style is to have the opening brace separately on a new line.

> +       memset((char *)mtd->priv + instr->addr, 0xff, instr->len);
> +       instr->state = MTD_ERASE_DONE;
> +       mtd_erase_callback(instr);
> +       return 0;
> +}
> +
> +static int ram_write(struct mtd_info *mtd, loff_t to, size_t len,
> +                               size_t *retlen, const u_char *buf) {
> +       memcpy((char*)mtd->priv + to, buf, len);
> +       *retlen = len;
> +       return 0;
> +}
> +
> +static int ram_read(struct mtd_info *mtd, loff_t from, size_t len,
> +               size_t *retlen, u_char *buf) {
> +       memcpy(buf, mtd->priv + from, len);
> +       *retlen = len;
> +       return 0;
> +}
> +
> +static int mtdram_probe(struct device_d *dev) {
> +       void __iomem *base;
> +       int device_id;
> +       struct mtd_info *mtd;
> +       struct resource *res;
> +       loff_t size;
> +       int ret = 0;
> +
> +
> +       mtd = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
> +       if (!mtd) {
> +               ret = -ENOMEM;
> +               goto nomem1;
> +       }

You could use xzalloc here and skip the return check.

> +
> +       device_id = DEVICE_ID_SINGLE;
> +       if (dev->device_node) {
> +               const char *alias = of_alias_get(dev->device_node);
> +               dev_info (dev, "is alias for %s\n", alias);
> +               if (alias)
> +                       mtd->name = xstrdup(alias);
> +       }
> +
> +       if (!mtd->name) {
> +               device_id = DEVICE_ID_DYNAMIC;
> +               mtd->name = "mtdram";
> +       }
> +
> +       dev_info(dev, "MTDRAM: probe for %s (dev_name=%s)\n",
> dev->name, mtd->name);

Your mailer wraps the lines. Can you change that? I won't be able to
apply this patch otherwise.

The driver seems a bit verbose. Can you limit the information printed in
the normal case to a single line?

Sascha

-- 
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