Re: [PATCH] USB: add USB test and measurement class driver
From: Oliver Neukum
Date: Wed Aug 27 2008 - 04:12:10 EST
Am Mittwoch 27 August 2008 02:05:01 schrieb Greg KH:
> +static ssize_t usbtmc_read(struct file *filp, char __user *buf,
> + size_t count, loff_t *f_pos)
> +{
> + struct usbtmc_device_data *data;
> + struct device *dev;
> + unsigned long int n_characters;
> + u8 *buffer;
> + int actual;
> + int done;
> + int remaining;
> + int retval;
> + int this_part;
> +
> + /* Get pointer to private data structure */
> + data = filp->private_data;
> + dev = &data->intf->dev;
> + buffer = data->buffer;
> +
> + remaining = count;
> + done = 0;
> +
> + while (remaining > 0) {
> + if (remaining > USBTMC_SIZE_IOBUFFER - 12 - 3)
> + this_part = USBTMC_SIZE_IOBUFFER - 12 - 3;
> + else
> + this_part = remaining;
> +
> + /* Setup IO buffer for DEV_DEP_MSG_IN message
> + * Refer to class specs for details
> + */
> + buffer[0] = 2;
> + buffer[1] = data->bTag;
> + buffer[2] = ~(data->bTag);
> + buffer[3] = 0; /* Reserved */
> + buffer[4] = (this_part - 12 - 3) & 255;
> + buffer[5] = ((this_part - 12 - 3) >> 8) & 255;
> + buffer[6] = ((this_part - 12 - 3) >> 16) & 255;
> + buffer[7] = ((this_part - 12 - 3) >> 24) & 255;
> + buffer[8] = data->TermCharEnabled * 2;
> + /* Use term character? */
> + buffer[9] = data->TermChar;
> + buffer[10] = 0; /* Reserved */
> + buffer[11] = 0; /* Reserved */
This function will go bad if concurrent readers enter, yet it has no locking.
Regards
Oliver
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