linux-kernel - Re: SPI read problem

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Message-ID: <BANLkTi=9dROLwWH2J=Y_FmP+t=rkjMLBJg@mail.gmail.com>
Date:	Wed, 20 Apr 2011 13:40:06 +0900
From:	"Murali K. Vemuri" <vemuri.muralikrishna@...il.com>
To:	徐建辉 <xujianhui168@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: SPI read problem

On Wed, Apr 20, 2011 at 12:19 PM, 徐建辉 <xujianhui168@...il.com> wrote:
> you can use tasklet.
>
> 2011/4/19 Murali K. Vemuri <vemuri.muralikrishna@...il.com>
>>
>> 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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>
>

Hi there,

I tried using "tasklet", "workqueue" and semaphore ... all my attempts failed.
if there is any other method I should try, please let me know.
Thanks & regards
Murali
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