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SubjectRe: [PATCHv3] drivers/misc: Altera active serial implementation
On 11/15/2010 09:23 AM, Baruch Siach wrote:
> --- /dev/null
> +++ b/drivers/misc/altera_as.c
> @@ -0,0 +1,349 @@
...
> +struct altera_as_device {
> + unsigned id;
> + struct device *dev;
> + struct miscdevice miscdev;
> + struct mutex open_lock;
> + struct gpio gpios[AS_GPIO_NUM];
> +};
> +
> +/*
> + * The only functions updating this array are .probe/.remove, which are
> + * serialized. Hence, no locking is needed here.
> + */
> +static struct {
> + int minor;

Why you need minor here? It's in drvdata->miscdev.minor.

> + struct altera_as_device *drvdata;
> +} altera_as_devs[AS_MAX_DEVS];

You don't need the struct at all.
static struct altera_as_device *drvdata[AS_MAX_DEVS];
should be enough.

> +static int altera_as_open(struct inode *inode, struct file *file)
> +{
> + int ret;
> + struct altera_as_device *drvdata = get_as_dev(iminor(inode));
> +
> + if (drvdata == NULL)
> + return -ENODEV;
> + file->private_data = drvdata;
> +
> + ret = mutex_trylock(&drvdata->open_lock);
> + if (ret == 0)
> + return -EBUSY;
> +
> + ret = gpio_request_array(drvdata->gpios, ARRAY_SIZE(drvdata->gpios));
> + if (ret < 0) {
> + mutex_unlock(&drvdata->open_lock);
> + return ret;
> + }

So leaving to userspace with mutex held. This is *wrong*. use
test_and_set_bit or alike instead.

> + return 0;
> +}
> +
> +static ssize_t altera_as_write(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
...
> + while ((count - written) > 0) {
> + err = copy_from_user(page_buf, buf+written, AS_PAGE_SIZE);
> + if (err < 0) {
> + err = -EFAULT;
> + goto out;
> + }
> +
> + xmit_cmd(drvdata->gpios, AS_WRITE_ENABLE);
> +
> + gpio_set_value(drvdata->gpios[ASIO_NCS].gpio, 0);
> + /* op code */
> + xmit_byte(drvdata->gpios, AS_PAGE_PROGRAM);
> + /* address */
> + xmit_byte(drvdata->gpios, (*ppos >> 16) & 0xff);
> + xmit_byte(drvdata->gpios, (*ppos >> 8) & 0xff);
> + xmit_byte(drvdata->gpios, *ppos & 0xff);
> + /* page data (LSB first) */
> + for (i = 0; i < AS_PAGE_SIZE; i++)
> + xmit_byte(drvdata->gpios, bitrev8(page_buf[i]));
> + gpio_set_value(drvdata->gpios[ASIO_NCS].gpio, 1);
> + mdelay(7);

So if I write 100 pages, I will _spin_ for 700 ms. You should rather
(m)sleep here.

> +
> + *ppos += AS_PAGE_SIZE;
> + written += AS_PAGE_SIZE;
> + }
> +
> +out:
> + kfree(page_buf);
> + return err ?: written;
> +}
...
> +static int __init altera_as_probe(struct platform_device *pdev)
> +{
...
> + drvdata->miscdev.minor = MISC_DYNAMIC_MINOR;
> + drvdata->miscdev.name = kasprintf(GFP_KERNEL, "altera_as%d",
> + pdata->id);
> + if (drvdata->miscdev.name == NULL)
> + return -ENOMEM;
> + drvdata->miscdev.fops = &altera_as_fops;
> + if (misc_register(&drvdata->miscdev) < 0) {

Hmm, how many devices can be in the system? This doesn't look like the
right way.

> + kfree(drvdata->miscdev.name);
> + return -ENODEV;
> + }
> + altera_as_devs[pdata->id].minor = drvdata->miscdev.minor;
> + altera_as_devs[pdata->id].drvdata = drvdata;

So now the device is usable without the mutex and gpios inited?

> + mutex_init(&drvdata->open_lock);
> +
> + drvdata->id = pdata->id;
> +
> + drvdata->gpios[ASIO_DATA].gpio = pdata->data;
> + drvdata->gpios[ASIO_DATA].flags = GPIOF_IN;
> + drvdata->gpios[ASIO_DATA].label = "as_data";
...
> + drvdata->gpios[ASIO_NCE].gpio = pdata->nce;
> + drvdata->gpios[ASIO_NCE].flags = GPIOF_OUT_INIT_HIGH;
> + drvdata->gpios[ASIO_NCE].label = "as_nce";
> +
> + dev_info(drvdata->dev, "Altera Cyclone Active Serial driver\n");
> +
> + return 0;
> +}

regards,
--
js
suse labs


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