2

For one of my applications, I have to understand the the SATA device driver flow. As per my understanding, SATA device driver should be there in the Linux kernel tree. I have referred how to find the driver module associated with a device on Linux to find the device driver for the SATA device. 

$ readlink /sys/block/sda/device/driver ../../../../../../../bus/scsi/d

I have go to the above location but haven't found a device driver file.

usr@usr:/sys/bus/scsi/drivers/sd$ ll
total 0
drwxr-xr-x 2 root root    0 Dec  9 17:00 ./
drwxr-xr-x 4 root root    0 Dec  9 17:00 ../
lrwxrwxrwx 1 root root    0 Dec  9 17:47 2:0:1:0 -> ../../../../devices/pci0000:00/0000:00:1f.2/ata3/host2/target2:0:1/2:0:1:0/
--w------- 1 root root 4096 Dec  9 17:47 bind
--w------- 1 root root 4096 Dec  9 17:47 uevent
--w------- 1 root root 4096 Dec  9 17:47 unbind
usr@usr:/sys/bus/scsi/drivers/sd$

Please suggest how can I see the device driver which was actually load for SATA hard drive on my system.

|improve this question
  • First take a look at lsmod. What distribution and kernel, please? – Faheem Mitha Dec 18 '15 at 9:48
  • I am using "Linux version 3.13.0-32-generic (buildd@phianna) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #57~precise1-Ubuntu SMP Tue Jul 15 03:51:20 UTC 2014" ubuntu 12.04 . Can you please elaborate what information I need to check in lsmod? – Hemant Dec 18 '15 at 9:53
  • Hemant, if you are using a stock Ubuntu kernel, and it sounds like you are, much of the functionality is in modules, to make the stock kernel as flexible as possible. So, take a look at the listed module names to see which one is implementing SATA. I seem to remember it is sg (tldp.org/HOWTO/SCSI-2.4-HOWTO/sg.html), but just do a search for "moulestring linux kernel module" for possible likely strings. – Faheem Mitha Dec 18 '15 at 10:00
  • See unix.stackexchange.com/a/6968/4671. This question might be a dupe of that. – Faheem Mitha Dec 18 '15 at 10:02
  • Hey,Thanks for the help, my final goal is to understand the software flow between the SATA Host(HBA) and a SATA device driver(SATA Hard Disk).To understand the flow I need to go through the SATA Host and Device driver code .I know AHCI can be used as a HBA in linux kernel which is at "linux-xlnx-xilinx_v2.6.30/drivers/ata/" but I am not sure about the SATA device driver.Can you point out which device driver code should I look in kernel tree to understand the device code flow or Can you point me somewhere I can get the sample SATA device driver code to undestand Host and Device communication? – Hemant Dec 18 '15 at 10:33
4

Use udevadm info as described in the other answer to the link you mentioned. Here's an example with a different grep-variant to reduce the output, while walking the /sys tree backwards:

$ udevadm info -a -n /dev/sda | egrep 'looking|DRIVER'
  looking at device '/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/block/sda':
    DRIVER==""
  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0':
    DRIVERS=="sd"
  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0':
    DRIVERS==""
  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1/host0':
    DRIVERS==""
  looking at parent device '/devices/pci0000:00/0000:00:1f.2/ata1':
    DRIVERS==""
  looking at parent device '/devices/pci0000:00/0000:00:1f.2':
    DRIVERS=="ahci"
  looking at parent device '/devices/pci0000:00':
    DRIVERS==""

So you can see that on my system, /dev/sda maps to SCSI device 0:0:0:0, which is attached to ata1 on PCI device 0:00:1f.2 (which is the host adapter)

The driver sd is responsible for handling the block device, while the driver ahci is responsible for handling the SATA host adapter.

|improve this answer
  • Thank for Answer. This helps a lot and I can find any device driver associate with any device on system with this method of course with a little change in the command argument. – Hemant Feb 9 '17 at 6:18
0

This only attempts to answer part of the question, namely how to find kernel driver code. I'd add this as a comment, but it's too long for one.

First install the Debian kernel sources package.

apt-get install linux-source-3.16

or whatever the corresponding version of your kernel is. Then the source is installed to /usr/src/linux-source-3.16.tar.xz.

Now create the /usr/local/src/linux directory and copy your source there. Namely:

mkdir /usr/local/src/linux

followed by

cp -ar /usr/src/linux-source-3.16.tar.xz /usr/local/src/linux

Now you can unpack it with tar.

tar xvf linux-source-3.16.tar.xz 
cd linux-source-3.16

Then run find for your desired device driver, say:

/usr/local/src/linux/linux-source-3.16$ find . -name 'sg.c'
./drivers/scsi/sg.c

So the driver in question is in 

/usr/local/src/linux/linux-source-3.16/drivers/scsi/sg.c

All the modules listed in lsmod should be in the source tree, in the form modname.c, where modname is the name that appears in the lsmod listing.

|improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.