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SubjectRe: [PATCH] power: supply: sbs-battery: simplify DT parsing
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G'day Arnd,

Sorry for the delay.
Been distracted and just catching up on mail I was just getting back to
implementing basically this same thing as requested by Sebastian when I saw your change.

Couple of comments below, I haven't tested it.


On 6/09/2016 21:16, Arnd Bergmann wrote:
> After the change to use the gpio descriptor interface, we get a warning if
> -Wmaybe-uninitialized is added back to the build flags (it is currently
> disabled:
>
> drivers/power/supply/sbs-battery.c: In function 'sbs_probe':
> drivers/power/supply/sbs-battery.c:760:28: error: 'pdata' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>
> The problem is that if neither the DT properties nor a platform_data
> pointer are provided, the chip->pdata pointer gets set to an uninitialized
> value.
>
> Looking at the code some more, I found that the sbs_of_populate_pdata
> function is more complex than necessary and has confusing calling
> conventions of possibly returning a valid pointer, a NULL pointer
> or an ERR_PTR pointer (in addition to the uninitialized pointer).
>
> To fix all of that, this gets rid of the chip->pdata pointer and
> simply moves the two integers into the sbs_info structure. This
> makes it much clearer from reading sbs_probe() what the precedence
> of the three possible values are (pdata, DT, hardcoded defaults)
> and completely avoids the #ifdef CONFIG_OF guards as
> of_property_read_u32() gets replaced with a compile-time stub
> when that is disabled, and returns an error if passed a NULL of_node
> pointer.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 3b5dd3a49496 ("power: supply: sbs-battery: Use gpio_desc and sleeping calls for battery detect")
> ---
> drivers/power/supply/sbs-battery.c | 98 ++++++++++++--------------------------
> 1 file changed, 31 insertions(+), 67 deletions(-)
>
> diff --git a/drivers/power/supply/sbs-battery.c b/drivers/power/supply/sbs-battery.c
> index 8b4c6a8681b0..248a5dd75e22 100644
> --- a/drivers/power/supply/sbs-battery.c
> +++ b/drivers/power/supply/sbs-battery.c
> @@ -169,6 +169,8 @@ struct sbs_info {
> bool enable_detection;
> int last_state;
> int poll_time;
> + int i2c_retry_count;
> + int poll_retry_count;
> struct delayed_work work;
> int ignore_changes;
> };
Done we need to remove pdata from here now. It's not set in the probe funciton anymore.

> @@ -184,7 +186,7 @@ static int sbs_read_word_data(struct i2c_client *client, u8 address)
> int retries = 1;
>
> if (chip->pdata)
> - retries = max(chip->pdata->i2c_retry_count + 1, 1);
> + retries = max(chip->i2c_retry_count + 1, 1);
I don't think this is quite right. as pdata is never set, condition needs to removed.

>
> while (retries > 0) {
> ret = i2c_smbus_read_word_data(client, address);
> @@ -212,8 +214,8 @@ static int sbs_read_string_data(struct i2c_client *client, u8 address,
> u8 block_buffer[I2C_SMBUS_BLOCK_MAX + 1];
>
> if (chip->pdata) {
> - retries_length = max(chip->pdata->i2c_retry_count + 1, 1);
> - retries_block = max(chip->pdata->i2c_retry_count + 1, 1);
> + retries_length = max(chip->i2c_retry_count + 1, 1);
> + retries_block = max(chip->i2c_retry_count + 1, 1);
> }
ditto

>
> /* Adapter needs to support these two functions */
> @@ -279,7 +281,7 @@ static int sbs_write_word_data(struct i2c_client *client, u8 address,
> int retries = 1;
>
> if (chip->pdata)
> - retries = max(chip->pdata->i2c_retry_count + 1, 1);
> + retries = max(chip->i2c_retry_count + 1, 1);
ditto
>
> while (retries > 0) {
> ret = i2c_smbus_write_word_data(client, address,
> @@ -741,61 +743,6 @@ static void sbs_delayed_work(struct work_struct *work)
> }
> }
>
> -#if defined(CONFIG_OF)
> -
> -#include <linux/of_device.h>
> -#include <linux/of_gpio.h>
> -
> -static const struct of_device_id sbs_dt_ids[] = {
> - { .compatible = "sbs,sbs-battery" },
> - { .compatible = "ti,bq20z75" },
> - { }
> -};
> -MODULE_DEVICE_TABLE(of, sbs_dt_ids);
> -
> -static struct sbs_platform_data *sbs_of_populate_pdata(struct sbs_info *chip)
> -{
> - struct i2c_client *client = chip->client;
> - struct device_node *of_node = client->dev.of_node;
> - struct sbs_platform_data *pdata;
> - int rc;
> - u32 prop;
> -
> - /* verify this driver matches this device */
> - if (!of_node)
> - return NULL;
> -
> - /* first make sure at least one property is set, otherwise
> - * it won't change behavior from running without pdata.
> - */
> - if (!of_get_property(of_node, "sbs,i2c-retry-count", NULL) &&
> - !of_get_property(of_node, "sbs,poll-retry-count", NULL))
> - goto of_out;
> -
> - pdata = devm_kzalloc(&client->dev, sizeof(struct sbs_platform_data),
> - GFP_KERNEL);
> - if (!pdata)
> - return ERR_PTR(-ENOMEM);
> -
> - rc = of_property_read_u32(of_node, "sbs,i2c-retry-count", &prop);
> - if (!rc)
> - pdata->i2c_retry_count = prop;
> -
> - rc = of_property_read_u32(of_node, "sbs,poll-retry-count", &prop);
> - if (!rc)
> - pdata->poll_retry_count = prop;
> -
> -of_out:
> - return pdata;
> -}
> -#else
> -static struct sbs_platform_data *sbs_of_populate_pdata(
> - struct sbs_info *client)
> -{
> - return ERR_PTR(-ENOSYS);
> -}
> -#endif
> -
> static const struct power_supply_desc sbs_default_desc = {
> .type = POWER_SUPPLY_TYPE_BATTERY,
> .properties = sbs_properties,
> @@ -838,13 +785,23 @@ static int sbs_probe(struct i2c_client *client,
> chip->ignore_changes = 1;
> chip->last_state = POWER_SUPPLY_STATUS_UNKNOWN;
>
> - if (!pdata)
> - pdata = sbs_of_populate_pdata(chip);
> -
> - if (IS_ERR(pdata))
> - return PTR_ERR(pdata);
> -
> - chip->pdata = pdata;
No longer set here.

> + /* use pdata if available, fall back to DT properties,
> + * or hardcoded defaults if not
> + */
> + rc = of_property_read_u32(client->dev.of_node, "sbs,i2c-retry-count",
> + &chip->i2c_retry_count);
> + if (rc)
> + chip->i2c_retry_count = 1;
> +
> + rc = of_property_read_u32(client->dev.of_node, "sbs,poll-retry-count",
> + &chip->poll_retry_count);
> + if (rc)
> + chip->poll_retry_count = 0;
> +
> + if (pdata) {
> + chip->poll_retry_count = pdata->poll_retry_count;
> + chip->i2c_retry_count = pdata->i2c_retry_count;
> + }
>
> chip->gpio_detect = devm_gpiod_get_optional(&client->dev,
> "sbs,battery-detect", GPIOD_IN);
> @@ -953,13 +910,20 @@ static const struct i2c_device_id sbs_id[] = {
> };
> MODULE_DEVICE_TABLE(i2c, sbs_id);
>
> +static const struct of_device_id sbs_dt_ids[] = {
> + { .compatible = "sbs,sbs-battery" },
> + { .compatible = "ti,bq20z75" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, sbs_dt_ids);
> +
> static struct i2c_driver sbs_battery_driver = {
> .probe = sbs_probe,
> .remove = sbs_remove,
> .id_table = sbs_id,
> .driver = {
> .name = "sbs-battery",
> - .of_match_table = of_match_ptr(sbs_dt_ids),
> + .of_match_table = sbs_dt_ids,
> .pm = SBS_PM_OPS,
> },
> };
>


Also sbs_external_power_changed is still referencing chip->pdata->poll_retry_count.
Which I think will result in null pointer dereference now.


--
Regards
Phil Reid


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