linux-kernel - Re: [PATCH 11/16 v2] Input: atmel_mxt_ts

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Date:	Fri, 13 Apr 2012 11:11:47 +0200
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Daniel Kurtz <djkurtz@...omium.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Nick Dyer <nick.dyer@...ev.co.uk>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, Benson Leung <bleung@...omium.org>,
	Yufeng Shen <miletus@...omium.org>
Subject: Re: [PATCH 11/16 v2] Input: atmel_mxt_ts - refactor reading object
 table

Hi Daniel,

> Instead of reading each object separately, fetch the whole table in one
> large i2c transaction.  A 6 byte table object requires 10 bytes to read,
> so doing this dramatically reduces overhead.
> 
> Also, as a cleanup, move object_table allocation (and post-fw-update
> reallocation) into mxt_get_object_table().
> 
> Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
> ---
>  drivers/input/touchscreen/atmel_mxt_ts.c |   66 +++++++++++++++---------------
>  1 files changed, 33 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> index 9d88faf..0d0dab6 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -437,14 +437,7 @@ static int mxt_write_reg(struct i2c_client *client, u16 reg, u16 len,
>  	return 0;
>  }
>  
> -static int mxt_read_object_table(struct i2c_client *client,
> -				      u16 reg, u8 *object_buf)
> -{
> -	return mxt_read_reg(client, reg, MXT_OBJECT_SIZE, object_buf);
> -}
> -
> -static struct mxt_object *
> -mxt_get_object(struct mxt_data *data, u8 type)
> +static struct mxt_object *mxt_get_object(struct mxt_data *data, u8 type)
>  {
>  	struct mxt_object *object;
>  	int i;
> @@ -733,25 +726,41 @@ static void mxt_handle_pdata(struct mxt_data *data)
>  
>  static int mxt_get_object_table(struct mxt_data *data)
>  {
> +	struct i2c_client *client = data->client;
> +	struct device *dev = &client->dev;
>  	int error;
>  	int i;
> -	u16 reg;
>  	u8 reportid = 0;
> -	u8 buf[MXT_OBJECT_SIZE];
> +	u8 *buf;
> +	size_t buf_size;
>  
> -	for (i = 0; i < data->info.object_num; i++) {
> -		struct mxt_object *object = data->object_table + i;
> +	/* Free old object table, if there was one. */
> +	kfree(data->object_table);
> +	data->object_table = kcalloc(data->info.object_num,
> +				     sizeof(struct mxt_object), GFP_KERNEL);
> +	if (!data->object_table) {
> +		dev_err(dev, "Failed to allocate object table\n");
> +		return -ENOMEM;
> +	}
>  
> -		reg = MXT_OBJECT_START + MXT_OBJECT_SIZE * i;
> -		error = mxt_read_object_table(data->client, reg, buf);
> -		if (error)
> -			return error;
> +	buf_size = MXT_OBJECT_SIZE * data->info.object_num;
> +	buf = kmalloc(buf_size, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> -		object->type = buf[0];
> -		object->start_address = (buf[2] << 8) | buf[1];
> -		object->size = buf[3] + 1;
> -		object->instances = buf[4] + 1;
> -		object->num_report_ids = buf[5];
> +	error = mxt_read_reg(client, MXT_OBJECT_START, buf_size, buf);
> +	if (error)
> +		goto done;
> +
> +	for (i = 0; i < data->info.object_num; i++) {
> +		struct mxt_object *object = &data->object_table[i];
> +		u8 *obj_buf = &buf[i * MXT_OBJECT_SIZE];
> +
> +		object->type = obj_buf[0];
> +		object->start_address = (obj_buf[2] << 8) | obj_buf[1];
> +		object->size = obj_buf[3] + 1;
> +		object->instances = obj_buf[4] + 1;
> +		object->num_report_ids = obj_buf[5];

Putting this conversion in a function would be nice, it would also
make it clear that the inverse, used for writing, is currently
missing. Alternatively, how about making the object struct actually
match the read data? To top it off, one could introduce a collection,
prepending the buffer size, making the write operation trivial.

struct mxt_raw_object {
	u8 type;
	__le16 start_address_le;
	u8 size_minus_one;
	u8 instances_minus_one;
	u8 num_report_ids;
};

struct mxt_raw_object_collection {
       __le16 total_bytes_le;
       struct mxt_raw_object instance[MAX_NUM_OBJECTS];
};

>  
>  		if (object->num_report_ids) {
>  			reportid += object->num_report_ids * object->instances;
> @@ -759,7 +768,9 @@ static int mxt_get_object_table(struct mxt_data *data)
>  		}
>  	}
>  
> -	return 0;
> +done:
> +	kfree(buf);
> +	return error;
>  }
>  
>  static int mxt_initialize(struct mxt_data *data)
> @@ -774,14 +785,6 @@ static int mxt_initialize(struct mxt_data *data)
>  	if (error)
>  		return error;
>  
> -	data->object_table = kcalloc(info->object_num,
> -				     sizeof(struct mxt_object),
> -				     GFP_KERNEL);
> -	if (!data->object_table) {
> -		dev_err(&client->dev, "Failed to allocate memory\n");
> -		return -ENOMEM;
> -	}
> -
>  	/* Get object table information */
>  	error = mxt_get_object_table(data);
>  	if (error)
> @@ -971,9 +974,6 @@ static ssize_t mxt_update_fw_store(struct device *dev,
>  		/* Wait for reset */
>  		msleep(MXT_FWRESET_TIME);
>  
> -		kfree(data->object_table);
> -		data->object_table = NULL;
> -
>  		mxt_initialize(data);
>  	}
>  
> -- 
> 1.7.7.3
> 

Thanks,
Henrik
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