Re: [PATCH 2.6.21-rc4] hwmon: HP Mobile Data Protection System 3D ACPI driver

Arjan van de Ven
2007-03-23T21:26:57Z

Hi,

your code looks very nice and clean, only few comments, see below

> +static int mdps_joystick_kthread(void *data)
> +{
> + int x = 0, y = 0, z = 0;
> +
> + while (!kthread_should_stop()) {
> + if (input_3d) {
> + mdps_get_xyz(mdps.device->handle, &x, &y, &z);
> + input_report_abs(mdps.idev, ABS_Z, z - mdps.zcalib);
> + } else
> + mdps_get_xy(mdps.device->handle, &x, &y);
> +
> + input_report_abs(mdps.idev, ABS_X, x - mdps.xcalib);
> + input_report_abs(mdps.idev, ABS_Y, y - mdps.ycalib);
> +
> + input_sync(mdps.idev);
> +
> + try_to_freeze();
> + msleep_interruptible(MDPS_POLL_INTERVAL);
> + }

what if you get a signal? you probably at least want to handle that
somehow. Also, waking up every 30 miliseconds is going to suck up
power ... but that might not be avoidable I suppose if you have to poll
the hardware.

> +static int mdps_misc_open(struct inode *inode, struct file *file)
> +{
> + int ret;
> +
> + if (!atomic_dec_and_test(&mdps.available)) {
> + atomic_inc(&mdps.available);
> + return -EBUSY; /* already open */
> + }
I often get a bit nervous at seeing such "open me once" code, but it
might well be ok ... I'll let others comment

> +
> + atomic_set(&mdps.count, 0);
> +
> + ret = request_irq(mdps.irq, mdps_irq, 0, "mdps", mdps_irq);

don't you want to allow shared interrupts?

> + if (ret) {
> + printk(KERN_ERR "mdps: IRQ%d allocation failed\n", mdps.irq);
> + return -ENODEV;
> + }

wouldn't you want to inc the atomic in this case?

> +static ssize_t mdps_misc_read(struct file *file, char __user *buf,
> + size_t count, loff_t *pos)
> +{
> + DECLARE_WAITQUEUE(wait, current);
> + u32 data;
> + ssize_t retval = count;
> +
> + if (count != sizeof(u32))
> + return -EINVAL;
> +
> + add_wait_queue(&mdps.misc_wait, &wait);
> + for (;;) {
> + set_current_state(TASK_INTERRUPTIBLE);
> + data = atomic_xchg(&mdps.count, 0);
> + if (data)
> + break;
> +
> + if (file->f_flags & O_NONBLOCK) {
> + retval = -EAGAIN;
> + goto out;
> + }
> +
> + if (signal_pending(current)) {
> + retval = -ERESTARTSYS;
> + goto out;
> + }
> +
> + schedule();
> + }
> +
> + if (copy_to_user(buf, &data, sizeof(data)))

I'm not entirely sure you want to go into copy_to_user() with a
TASK_INTERRUPTIBLE state, I would feel a lot better if you did an
explicit __set_current_state(TASK_RUNNING) just before this.

> + retval = -EFAULT;
> +
> +out:
> + set_current_state(TASK_RUNNING);

.. which you do here anyway

> mdps_get_resource(struct acpi_resource *resource, void *context)
> +{
> + if (resource->type == ACPI_RESOURCE_TYPE_EXTENDED_IRQ) {
> + struct acpi_resource_extended_irq *irq;
> + u32 *device_irq = context;
> +
> + irq = &resource->data.extended_irq;
> + *device_irq = irq->interrupts[0];

eh wait.. if this thing gives you an interrupt.. why do you need to poll
every 30 msec? am I missing something?