linux-kernel - SPI read problem

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Message-ID: <BANLkTi=5peAF4v_2i4uFSqicWCGOqHMRaA@mail.gmail.com>
Date:	Wed, 20 Apr 2011 06:46:10 +0900
From:	"Murali K. Vemuri" <vemuri.muralikrishna@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: SPI read problem

Hello there,
I have a device which is Written_to/Read_from using SPI Bus.

I initialize the device like this:

static int __init myDEV_init(void)
{
   return spi_register_driver(&myDEV_driver);
}
module_init(myDEV_init);

My myDEV_probe() function looks like this:

static int __devinit myDEV_probe(struct spi_device *spi)
{
.....
.....
/*when my CPU receives a particular IRQ, I have to do a spi_read() and
do couple of spi_write(), I am using like this:*/
err = request_threaded_irq (MY_DEV_IRQ, NULL, myDEV_irq_thread,
           IRQF_TRIGGER_RISING, "MYDEV", NULL);

return 0;
}

When the Interrupt is received by the CPU, myDEV_irq_thread is being called.
However, in the ISR I have to do  spi_read(). This is always returning
"Timed out".

To verify if the device is not at all working, along with registering
for the IRQ, I also created a char device through I did a IOCTL.
The IOCTL command in turn does spi_read(). In this case spi_read() is
successful.

Since it is necessary to do spi_read() in my ISR, I searched around
and found some information that
spi_read() is callable only from contexts that can sleep.

How can I make my ISR sleep? or is there any other way of doing this?

Any help is highly appreciated.
Thanks & regards
Murali
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