Difference between revisions of "Linux drivers generalities"
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This page summarizes all the important things to know when talking about Linux drivers in general. | This page summarizes all the important things to know when talking about Linux drivers in general. | ||
| − | ==What== | + | ==What are they ?== |
Linux drivers are the piece of code running inside the kernel itself that are assigned to a specific peripheral driving. | Linux drivers are the piece of code running inside the kernel itself that are assigned to a specific peripheral driving. | ||
They can exist in 2 forms: | They can exist in 2 forms: | ||
| Line 7: | Line 7: | ||
* or they can be compiled as loadable modules (the famous .ko files) | * or they can be compiled as loadable modules (the famous .ko files) | ||
| − | When compiled as module (<M> in | + | ==How to use them== |
| + | When compiled as "static" ('''<*>''', in Linux menuconfig) they are integrated in the Linux image (''buildroot/binaries/apfxx/linux-kernel-2.6.xx-arm.bin''), so when you reflash your kernel, the driver are immediately available. But if you don't use them, they consume some place in memory (RAM). | ||
| + | |||
| + | When compiled as "module" ('''<M>''', in Linux menuconfig) they can be dynamically loaded at runtime, when necessary. For example if you need to load the FPGA at a particular time you can do a: | ||
| + | <pre class="apf"> | ||
# modprobe fpga_loader | # modprobe fpga_loader | ||
| + | </pre> | ||
or | or | ||
| − | # insmod /lib/modules/drivers/armadeus/fpga/fpga_loader.ko | + | <pre class="apf"> |
| + | # insmod /lib/modules/2.6.xx/drivers/armadeus/fpga/fpga_loader.ko | ||
| + | </pre> | ||
| + | |||
| + | ==Where should I copy modules ?== | ||
| + | ''modprobe'' knows where to find the corresponding .ko file and find all its dependencies thanks to the ''/lib/modules/2.6.2x/modules.dep'' file. So If you compile new drivers as module and copy them on your board "manually" (ie TFTP or NFS), don't forget to update ''/lib/modules/2.6.2x/modules.dep'' too. On your Host this file can be found in ''buildroot/project_build_armvxx/apfxx/root/lib/modules/2.6.2x/modules.dep''. | ||
| + | All modules are located in ''/lib/modules/2.6.xx/drivers/'' subdirectories on your target and ''buildroot/project_build_armvxx/apfxx/root/lib/modules/drivers'' on your Host. | ||
| − | + | [[Category:Linux drivers]] | |
Latest revision as of 22:42, 11 June 2009
This page summarizes all the important things to know when talking about Linux drivers in general.
What are they ?
Linux drivers are the piece of code running inside the kernel itself that are assigned to a specific peripheral driving. They can exist in 2 forms:
- they can be statically linked to the kernel image. In that case we refer to static drivers
- or they can be compiled as loadable modules (the famous .ko files)
How to use them
When compiled as "static" (<*>, in Linux menuconfig) they are integrated in the Linux image (buildroot/binaries/apfxx/linux-kernel-2.6.xx-arm.bin), so when you reflash your kernel, the driver are immediately available. But if you don't use them, they consume some place in memory (RAM).
When compiled as "module" (<M>, in Linux menuconfig) they can be dynamically loaded at runtime, when necessary. For example if you need to load the FPGA at a particular time you can do a:
# modprobe fpga_loader
or
# insmod /lib/modules/2.6.xx/drivers/armadeus/fpga/fpga_loader.ko
Where should I copy modules ?
modprobe knows where to find the corresponding .ko file and find all its dependencies thanks to the /lib/modules/2.6.2x/modules.dep file. So If you compile new drivers as module and copy them on your board "manually" (ie TFTP or NFS), don't forget to update /lib/modules/2.6.2x/modules.dep too. On your Host this file can be found in buildroot/project_build_armvxx/apfxx/root/lib/modules/2.6.2x/modules.dep. All modules are located in /lib/modules/2.6.xx/drivers/ subdirectories on your target and buildroot/project_build_armvxx/apfxx/root/lib/modules/drivers on your Host.
