Re: [PATCH v4 03/13] mmc: provide a standard MMC device-tree binding parser centrally

[Simon Horman <horms@verge.net.au>]

On Fri, Feb 15, 2013 at 04:13:52PM +0100, Guennadi Liakhovetski wrote:
> MMC defines a number of standard DT bindings. Having each driver parse
> them individually adds code redundancy and is error prone. Provide a
> standard function to unify the parsing. After all drivers are converted
> to using it instead of their own parsers, this function can be integrated
> into mmc_alloc_host().
> 
> Cc: Markus Pargmann <mpa@pengutronix.de>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> ---
> 
> v4: make the bus-width property optional to match a recent change to 
> mmc.txt, use of_property_read_bool() to obtain a boolean value of a DT 
> property, add comments.
> 
>  drivers/mmc/core/host.c  |  108 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mmc/host.h |    1 +
>  2 files changed, 109 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index ee2e16b..daa2ed1 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -15,6 +15,8 @@
>  #include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/idr.h>
> +#include <linux/of.h>
> +#include <linux/of_gpio.h>
>  #include <linux/pagemap.h>
>  #include <linux/export.h>
>  #include <linux/leds.h>
> @@ -23,6 +25,7 @@
>  
>  #include <linux/mmc/host.h>
>  #include <linux/mmc/card.h>
> +#include <linux/mmc/slot-gpio.h>
>  
>  #include "core.h"
>  #include "host.h"
> @@ -295,6 +298,111 @@ static inline void mmc_host_clk_sysfs_init(struct mmc_host *host)
>  #endif
>  
>  /**
> + *	mmc_of_parse() - parse host's device-tree node
> + *	@host: host, whose node should be parsed.
> + *
> + * To keep the rest of the MMC subsystem unaware of the fact, whether DT has
> + * been used to to instantiate and configure this host instance or not, we
> + * parse the properties and set respective generic mmc-host flags and
> + * parameters.
> + */
> +void mmc_of_parse(struct mmc_host *host)
> +{
> +	struct device_node *np;
> +	u32 bus_width;
> +	bool explicit_inv_wp, gpio_inv_wp = false;
> +	enum of_gpio_flags flags;
> +	int len, ret, gpio;
> +
> +	if (!host->parent || !host->parent->of_node)
> +		return;
> +
> +	np = host->parent->of_node;
> +
> +	/* "bus-width" is translated to MMC_CAP_*_BIT_DATA flags */
> +	if (of_property_read_u32_array(np, "bus-width", &bus_width, 1) < 0)
> +		dev_dbg(host->parent,
> +			"\"bus-width\" property is missing, assuming 1 bit.\n");
> +
> +	switch (bus_width) {

kbuild tells me that gcc thinks that bus_width is used without being
initialised here. Assuming that of_property_read_u32_array always
initialises bus_width if it returns zero then perhaps it would be worth
considering using uninitialized_var().

> +	case 8:
> +		host->caps |= MMC_CAP_8_BIT_DATA;
> +		/* Hosts, capable of 8-bit transfers can also do 4 bits */
> +	case 4:
> +		host->caps |= MMC_CAP_4_BIT_DATA;
> +		break;
> +	case 1:
> +		break;
> +	default:
> +		dev_err(host->parent,
> +			"Invalid \"bus-width\" value %ud!\n", bus_width);
> +	}
> +
> +	/* f_max is obtained from the optional "max-frequency" property */
> +	of_property_read_u32_array(np, "max-frequency", &host->f_max, 1);
> +
> +	/*
> +	 * Configure CD and WP pins. They are both by default active low to
> +	 * match the SDHCI spec. If GPIOs are provided for CD and / or WP, the
> +	 * mmc-gpio helpers are used to attach, configure and use them. If
> +	 * polarity inversion is specified in DT, one of MMC_CAP2_CD_ACTIVE_HIGH
> +	 * and MMC_CAP2_RO_ACTIVE_HIGH capability-2 flags is set. If the
> +	 * "broken-cd" property is provided, the MMC_CAP_NEEDS_POLL capability
> +	 * is set. If the "non-removable" property is found, the
> +	 * MMC_CAP_NONREMOVABLE capability is set and no card-detection
> +	 * configuration is performed.
> +	 */
> +
> +	/* Parse Card Detection */
> +	if (of_find_property(np, "non-removable", &len)) {
> +		host->caps |= MMC_CAP_NONREMOVABLE;
> +	} else {
> +		bool explicit_inv_cd, gpio_inv_cd = false;
> +
> +		explicit_inv_cd = of_property_read_bool(np, "cd-inverted");
> +
> +		if (of_find_property(np, "broken-cd", &len))
> +			host->caps |= MMC_CAP_NEEDS_POLL;
> +
> +		gpio = of_get_named_gpio_flags(np, "cd-gpios", 0, &flags);
> +		if (gpio_is_valid(gpio)) {
> +			if (!(flags & OF_GPIO_ACTIVE_LOW))
> +				gpio_inv_cd = true;
> +
> +			ret = mmc_gpio_request_cd(host, gpio);
> +			if (ret < 0)
> +				dev_err(host->parent,
> +					"Failed to request CD GPIO #%d: %d!\n",
> +					gpio, ret);
> +			else
> +				dev_info(host->parent, "Got CD GPIO #%d.\n",
> +					 gpio);
> +		}
> +
> +		if (explicit_inv_cd ^ gpio_inv_cd)
> +			host->caps2 |= MMC_CAP2_CD_ACTIVE_HIGH;
> +	}
> +
> +	/* Parse Write Protection */
> +	explicit_inv_wp = of_property_read_bool(np, "wp-inverted");
> +
> +	gpio = of_get_named_gpio_flags(np, "wp-gpios", 0, &flags);
> +	if (gpio_is_valid(gpio)) {
> +		if (!(flags & OF_GPIO_ACTIVE_LOW))
> +			gpio_inv_wp = true;
> +
> +		ret = mmc_gpio_request_ro(host, gpio);
> +		if (ret < 0)
> +			dev_err(host->parent,
> +				"Failed to request WP GPIO: %d!\n", ret);
> +	}
> +	if (explicit_inv_wp ^ gpio_inv_wp)
> +		host->caps2 |= MMC_CAP2_RO_ACTIVE_HIGH;
> +}
> +
> +EXPORT_SYMBOL(mmc_of_parse);
> +
> +/**
>   *	mmc_alloc_host - initialise the per-host structure.
>   *	@extra: sizeof private data structure
>   *	@dev: pointer to host device model structure
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 61a10c1..13c0c8d 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -345,6 +345,7 @@ extern struct mmc_host *mmc_alloc_host(int extra, struct device *);
>  extern int mmc_add_host(struct mmc_host *);
>  extern void mmc_remove_host(struct mmc_host *);
>  extern void mmc_free_host(struct mmc_host *);
> +void mmc_of_parse(struct mmc_host *host);
>  
>  static inline void *mmc_priv(struct mmc_host *host)
>  {
> -- 
> 1.7.2.5
>