Hi
a stupid question: is this fast?
Albert
On Tue, Dec 15, 2009 at 3:22 PM, Caglar Akyuz
<[email protected]>wrote:
> On Tuesday 15 December 2009 09:47:22 Albert Burbea wrote:
>
> > Hi everybody,
>
> Hi,
>
> > I would like to know how can I use an I2C device inside a device driver.
>
> > The problem is that I wish to leave the I2C available to other
> application
>
> > on the platform, and I do not wish to do add_driver every time I need
>
> > access to the I2C from the driver. Actually I need a handle that is
> always
>
> > open in the driver.
>
> I use something like this for my touchscreen driver:
>
> static int davinci_tsc2004_read(u8 size, u8 * val, u16 addr)
>
> {
>
> struct i2c_adapter *adap;
>
> int err;
>
> struct i2c_msg msg[1];
>
> adap = i2c_get_adapter(1);
>
> if (!adap)
>
> return -ENODEV;
>
> msg->addr = addr;
>
> msg->flags = I2C_M_RD;
>
> msg->len = size;
>
> msg->buf = val;
>
> err = i2c_transfer(adap, msg, 1);
>
> if (err >= 0)
>
> return 0;
>
> return err;
>
> }
>
> Write operation is smilar, just using 0 instead of I2C_M_RD.
>
> > Also, can I use the I2C driver in an isr handling code?
>
> I don't think so, though I don't known new threaded interrupt handlers.
>
> You should schedule a workqueue in your isr handler and use i2c calls in
> workqueue. Again from my touchscreendriver:
>
> static void tsc_workqueue_handler(struct work_struct *work)
>
> {
>
> /* Actual I2C stuff */
>
> }
>
> DECLARE_WORK(tsc_wq, tsc_workqueue_handler);
>
> static irqreturn_t tsc2004_ts_irq_handler(int irq, void *dev_id)
>
> {
>
> /*
>
> * Schedule the workqueue for I2C transfers
>
> */
>
> schedule_work(&tsc_wq);
>
> return IRQ_HANDLED;
>
> }
>
> Best regards,
>
> Caglar
>
--
Albert Burbea
Harishonim 8
Ramat Gan 52502, Israel
Tel/Fax + 972-3-7526016
Mobile: +972-52-3541842
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