How to use spi device from another kernel module?
Hello, I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module. Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c) Regards, Ran
On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module.
Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c)
Find out what's the SPI bus number (for the master) and the chip select on that SPI master (for the SPI device) Then you can use bus_for_each_device on spi_bus_type and find the spi_device you're looking for. See the following code for an example of how to use bus_for_each_device: http://lxr.free-electrons.com/source/drivers/spi/spi.c#L524 In your check function, just make sure your spi->master->bus_num is the bus you want and the spi->chip_select is the chip select corresponding to the device you want. If both these conditions are satisfied, there you have your spi_device. HTH, -Joel
On Tue, Dec 06, 2016 at 09:12:24PM -0800, Joel Fernandes wrote:
On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module.
Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c)
Find out what's the SPI bus number (for the master) and the chip select on that SPI master (for the SPI device)
Then you can use bus_for_each_device on spi_bus_type and find the spi_device you're looking for. See the following code for an example of how to use bus_for_each_device:
http://lxr.free-electrons.com/source/drivers/spi/spi.c#L524
In your check function, just make sure your spi->master->bus_num is the bus you want and the spi->chip_select is the chip select corresponding to the device you want. If both these conditions are satisfied, there you have your spi_device.
Eeek, no, please never do that, use the proper spi apis to get your needed device. They are there somewhere, using a "raw" bus_for_each_device is never the answer unless you are a bus and iterating over your own device list. thanks, greg k-h
On Wed, Dec 7, 2016 at 9:02 AM, Greg KH <greg@kroah.com> wrote:
On Tue, Dec 06, 2016 at 09:12:24PM -0800, Joel Fernandes wrote:
On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module.
Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c)
Find out what's the SPI bus number (for the master) and the chip select on that SPI master (for the SPI device)
Then you can use bus_for_each_device on spi_bus_type and find the spi_device you're looking for. See the following code for an example of how to use bus_for_each_device:
Thanks Joel, Though in this example I can't see how to used bus number & cs. Probably I ask for something which is not too proper, as Greg mentioned. Yet, I need to do that, as simple as possible...
In your check function, just make sure your spi->master->bus_num is the bus you want and the spi->chip_select is the chip select corresponding to the device you want. If both these conditions are satisfied, there you have your spi_device.
Eeek, no, please never do that, use the proper spi apis to get your needed device. They are there somewhere, using a "raw" bus_for_each_device is never the answer unless you are a bus and iterating over your own device list.
thanks,
greg k-h
Hi, I'm trying to understand how to get the spi device from proc entry. Is there any example which demonstrate such usage ? Thanks, Ran
On Tue, Dec 6, 2016 at 11:02 PM, Greg KH <greg@kroah.com> wrote:
On Tue, Dec 06, 2016 at 09:12:24PM -0800, Joel Fernandes wrote:
On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module.
Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c)
Find out what's the SPI bus number (for the master) and the chip select on that SPI master (for the SPI device)
Then you can use bus_for_each_device on spi_bus_type and find the spi_device you're looking for. See the following code for an example of how to use bus_for_each_device:
http://lxr.free-electrons.com/source/drivers/spi/spi.c#L524
In your check function, just make sure your spi->master->bus_num is the bus you want and the spi->chip_select is the chip select corresponding to the device you want. If both these conditions are satisfied, there you have your spi_device.
Eeek, no, please never do that, use the proper spi apis to get your needed device. They are there somewhere, using a "raw" bus_for_each_device is never the answer unless you are a bus and iterating over your own device list.
Yes I completely agree, maybe I assumed too much and thought he was trying to do this for some quick debugging from some kernel module, and was just looking for a quick and dirty way to get to a spi_device. Was not really suggesting this for production code. :) Regards, Joel
thanks,
greg k-h
On Wed, Dec 7, 2016 at 6:58 PM, Joel Fernandes <agnel.joel@gmail.com> wrote:
On Tue, Dec 6, 2016 at 11:02 PM, Greg KH <greg@kroah.com> wrote:
On Tue, Dec 06, 2016 at 09:12:24PM -0800, Joel Fernandes wrote:
On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module.
Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c)
Find out what's the SPI bus number (for the master) and the chip select on that SPI master (for the SPI device)
Then you can use bus_for_each_device on spi_bus_type and find the spi_device you're looking for. See the following code for an example of how to use bus_for_each_device:
http://lxr.free-electrons.com/source/drivers/spi/spi.c#L524
In your check function, just make sure your spi->master->bus_num is the bus you want and the spi->chip_select is the chip select corresponding to the device you want. If both these conditions are satisfied, there you have your spi_device.
Eeek, no, please never do that, use the proper spi apis to get your needed device. They are there somewhere, using a "raw" bus_for_each_device is never the answer unless you are a bus and iterating over your own device list.
Yes I completely agree, maybe I assumed too much and thought he was trying to do this for some quick debugging from some kernel module, and was just looking for a quick and dirty way to get to a spi_device. Was not really suggesting this for production code. :)
You were actually Right... That's exactly what I wanted :) , so I probably will try to use your simple method. I think that for production , spidev shows a good example how to use spi as a char device: https://github.com/Xilinx/linux-xlnx/blob/master/drivers/spi/spidev.c Thanks! Ran
Regards, Joel
thanks,
greg k-h
On Wed, Dec 7, 2016 at 7:26 PM, Ran Shalit <ranshalit@gmail.com> wrote:
On Wed, Dec 7, 2016 at 6:58 PM, Joel Fernandes <agnel.joel@gmail.com> wrote:
On Tue, Dec 6, 2016 at 11:02 PM, Greg KH <greg@kroah.com> wrote:
On Tue, Dec 06, 2016 at 09:12:24PM -0800, Joel Fernandes wrote:
On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module.
Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c)
Find out what's the SPI bus number (for the master) and the chip select on that SPI master (for the SPI device)
Then you can use bus_for_each_device on spi_bus_type and find the spi_device you're looking for. See the following code for an example of how to use bus_for_each_device:
Hi, I did try using this method with the following call: bus_for_each_dev(&spi_bus_type, NULL, NULL, spi_device_found); static int spi_device_found(struct device *dev, void *data) { struct spi_device *spi = container_of(dev, struct spi_device, dev); printk(": %s %s %dkHz %d bits mode=0x%02X\n", spi->modalias, dev_name(dev), spi->max_speed_hz/1000, spi->bits_per_word, spi->mode); return 0; } But for some reason the list is empty, although I do have devices registered successfuly with spi_register_driver. Using the same method with i2c works well, not sure why it doesn't list anything with spi. Thanks, Ran
http://lxr.free-electrons.com/source/drivers/spi/spi.c#L524
In your check function, just make sure your spi->master->bus_num is the bus you want and the spi->chip_select is the chip select corresponding to the device you want. If both these conditions are satisfied, there you have your spi_device.
Eeek, no, please never do that, use the proper spi apis to get your needed device. They are there somewhere, using a "raw" bus_for_each_device is never the answer unless you are a bus and iterating over your own device list.
Yes I completely agree, maybe I assumed too much and thought he was trying to do this for some quick debugging from some kernel module, and was just looking for a quick and dirty way to get to a spi_device. Was not really suggesting this for production code. :)
You were actually Right... That's exactly what I wanted :) , so I probably will try to use your simple method. I think that for production , spidev shows a good example how to use spi as a char device: https://github.com/Xilinx/linux-xlnx/blob/master/drivers/spi/spidev.c
Thanks! Ran
Regards, Joel
thanks,
greg k-h
On Wed, Dec 7, 2016 at 8:21 PM, Ran Shalit <ranshalit@gmail.com> wrote:
On Wed, Dec 7, 2016 at 7:26 PM, Ran Shalit <ranshalit@gmail.com> wrote:
On Wed, Dec 7, 2016 at 6:58 PM, Joel Fernandes <agnel.joel@gmail.com> wrote:
On Tue, Dec 6, 2016 at 11:02 PM, Greg KH <greg@kroah.com> wrote:
On Tue, Dec 06, 2016 at 09:12:24PM -0800, Joel Fernandes wrote:
On Tue, Dec 6, 2016 at 11:42 AM, Ran Shalit <ranshalit@gmail.com> wrote:
Hello,
I have spi device which is registered using spi_register_board_info(), and I would like to get a pointer to this device in some other kernel module.
Is there a simple way to get a pointer to pointer to a device , so that we can use it from other module ? (something like i2c_get_adapter for i2c)
Find out what's the SPI bus number (for the master) and the chip select on that SPI master (for the SPI device)
Then you can use bus_for_each_device on spi_bus_type and find the spi_device you're looking for. See the following code for an example of how to use bus_for_each_device:
Hi,
I did try using this method with the following call:
bus_for_each_dev(&spi_bus_type, NULL, NULL, spi_device_found);
static int spi_device_found(struct device *dev, void *data) { struct spi_device *spi = container_of(dev, struct spi_device, dev);
printk(": %s %s %dkHz %d bits mode=0x%02X\n", spi->modalias, dev_name(dev), spi->max_speed_hz/1000, spi->bits_per_word, spi->mode);
return 0; }
But for some reason the list is empty, although I do have devices registered successfuly with spi_register_driver. Using the same method with i2c works well, not sure why it doesn't list anything with spi.
Thanks, Ran
http://lxr.free-electrons.com/source/drivers/spi/spi.c#L524
In your check function, just make sure your spi->master->bus_num is the bus you want and the spi->chip_select is the chip select corresponding to the device you want. If both these conditions are satisfied, there you have your spi_device.
Eeek, no, please never do that, use the proper spi apis to get your needed device. They are there somewhere, using a "raw" bus_for_each_device is never the answer unless you are a bus and iterating over your own device list.
Yes I completely agree, maybe I assumed too much and thought he was trying to do this for some quick debugging from some kernel module, and was just looking for a quick and dirty way to get to a spi_device. Was not really suggesting this for production code. :)
If I may please ask one more thing on this issue, just for my understanding. Before trying the above suggestions, I made the following trial (which I know is quick and dirty ):
I copied the pointer to spi device from probe() function into static variable and than tried to use it later (in proc/sysfs), but I get exceptions. I am not going to use this method anyway, yet I am curious why it doesn't work. Thank you, Ran
You were actually Right... That's exactly what I wanted :) , so I probably will try to use your simple method. I think that for production , spidev shows a good example how to use spi as a char device: https://github.com/Xilinx/linux-xlnx/blob/master/drivers/spi/spidev.c
Thanks! Ran
Regards, Joel
thanks,
greg k-h
participants (3)
-
Greg KH -
Joel Fernandes -
Ran Shalit