Re: [PATCH v8 2/4] power: reset: add reboot mode driver

[Krzysztof Kozlowski <k.kozlowski@samsung.com>]

On 04/25/2016 08:55 AM, Andy Yan wrote:
> This driver parses the reboot commands like "reboot bootloader"
> and "reboot recovery" to get a boot mode described in the
> device tree , then call the write interfae to store the boot
> mode in some place like special register or sram, which can
> be read by the bootloader after system reboot, then the bootloader
> can take different action according to the mode stored.
> 
> This is commonly used on Android based devices, in order to
> reboot the device into fastboot or recovery mode.
> 
> Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
> Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>
> Tested-by: John Stultz <john.stultz@linaro.org>
> Acked-by: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
> 
> ---
> 
> Changes in v8:
> - do some cleanup when driver ubind
> 
> Changes in v7:
> - address some suggestions from Krzysztof, make syscon-reboot-mode driver data self-contained.
> 
> Changes in v6: None
> Changes in v5:
> - use two blank space under help in Kconfig
> - use unsigned int instead of int for member magic in struct mode_info
> 
> Changes in v4:
> - make this driver depends on OF to avoid kbuild test error
> 
> Changes in v3:
> - scan multi properities
> - add mask value for some platform which only use some bits of the register
>   to store boot mode magic value
> 
> Changes in v2:
> - move to dir drivers/power/reset/
> - make syscon-reboot-mode a generic driver
> 
> Changes in v1:
> - fix the embarrassed compile warning
> - correct the maskrom magic number
> - check for the normal reboot
> 
>  drivers/power/reset/Kconfig              |  13 ++++
>  drivers/power/reset/Makefile             |   2 +
>  drivers/power/reset/reboot-mode.c        | 118 +++++++++++++++++++++++++++++++
>  drivers/power/reset/reboot-mode.h        |  14 ++++
>  drivers/power/reset/syscon-reboot-mode.c |  99 ++++++++++++++++++++++++++
>  5 files changed, 246 insertions(+)
>  create mode 100644 drivers/power/reset/reboot-mode.c
>  create mode 100644 drivers/power/reset/reboot-mode.h
>  create mode 100644 drivers/power/reset/syscon-reboot-mode.c
> 
> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> index 1131cf7..cf50630 100644
> --- a/drivers/power/reset/Kconfig
> +++ b/drivers/power/reset/Kconfig
> @@ -173,5 +173,18 @@ config POWER_RESET_ZX
>  	help
>  	  Reboot support for ZTE SoCs.
>  
> +config REBOOT_MODE
> +	tristate
> +
> +config SYSCON_REBOOT_MODE
> +	bool "Generic SYSCON regmap reboot mode driver"
> +	depends on OF
> +	select REBOOT_MODE
> +	help
> +	  Say y here will enable reboot mode driver. This will
> +	  get reboot mode arguments and store it in SYSCON mapped
> +	  register, then the bootloader can read it to take different
> +	  action according to the mode.
> +
>  endif
>  
> diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
> index 096fa67..a63865b 100644
> --- a/drivers/power/reset/Makefile
> +++ b/drivers/power/reset/Makefile
> @@ -20,3 +20,5 @@ obj-$(CONFIG_POWER_RESET_SYSCON) += syscon-reboot.o
>  obj-$(CONFIG_POWER_RESET_SYSCON_POWEROFF) += syscon-poweroff.o
>  obj-$(CONFIG_POWER_RESET_RMOBILE) += rmobile-reset.o
>  obj-$(CONFIG_POWER_RESET_ZX) += zx-reboot.o
> +obj-$(CONFIG_REBOOT_MODE) += reboot-mode.o
> +obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o
> diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
> new file mode 100644
> index 0000000..cdc4d72
> --- /dev/null
> +++ b/drivers/power/reset/reboot-mode.c
> @@ -0,0 +1,118 @@
> +/*
> + * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
> + *
> + * 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.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/reboot.h>
> +#include "reboot-mode.h"
> +
> +#define PREFIX "mode-"
> +
> +struct mode_info {
> +	const char *mode;
> +	unsigned int magic;
> +	struct list_head list;
> +};
> +
> +static int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
> +				 const char *cmd)
> +{
> +	const char *normal = "normal";
> +	int magic = 0;
> +	struct mode_info *info;
> +
> +	if (!cmd)
> +		cmd = normal;
> +
> +	list_for_each_entry(info, &reboot->head, list) {
> +		if (!strcmp(info->mode, cmd)) {
> +			magic = info->magic;
> +			break;
> +		}
> +	}
> +
> +	return magic;
> +}
> +
> +static int reboot_mode_notify(struct notifier_block *this,
> +			      unsigned long mode, void *cmd)
> +{
> +	struct reboot_mode_driver *reboot;
> +	int magic;
> +
> +	reboot = container_of(this, struct reboot_mode_driver, reboot_notifier);
> +	magic = get_reboot_mode_magic(reboot, cmd);
> +	if (magic)
> +		reboot->write(reboot, magic);
> +
> +	return NOTIFY_DONE;
> +}
> +
> +int reboot_mode_register(struct reboot_mode_driver *reboot)
> +{
> +	struct mode_info *info;
> +	struct property *prop;
> +	struct device_node *np = reboot->dev->of_node;
> +	size_t len = strlen(PREFIX);
> +	int ret;
> +
> +	INIT_LIST_HEAD(&reboot->head);
> +
> +	for_each_property_of_node(np, prop) {
> +		if (len > strlen(prop->name) || strncmp(prop->name, PREFIX, len))
> +			continue;
> +
> +		info = devm_kzalloc(reboot->dev, sizeof(*info), GFP_KERNEL);
> +		if (!info) {
> +			ret = -ENOMEM;
> +			goto error;
> +		}
> +
> +		info->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
> +		if (of_property_read_u32(np, prop->name, &info->magic)) {
> +			dev_err(reboot->dev, "reboot mode %s without magic number\n",
> +				info->mode);
> +			devm_kfree(reboot->dev, info);

kfree_const(). The duplicated string won't be added to the list so it
won't be freed in error path or in unregister().

> +			continue;
> +		}
> +		list_add_tail(&info->list, &reboot->head);
> +	}
> +
> +	reboot->reboot_notifier.notifier_call = reboot_mode_notify;
> +	ret = register_reboot_notifier(&reboot->reboot_notifier);
> +	if (ret)
> +		dev_err(reboot->dev, "can't register reboot notifier\n");

I don't understand your error paths. In previous patches they were
buggy... they still look buggy, I think. It's 8th iteration and such
basic things are still present.

If this is an error then shouldn't everything be cleaned up? You are
returning error code thus the reboot_mode_register() caller will fail.
This means the probe will fail. So you need to clean up - go to error?

Best regards,
Krzysztof