[Intel-gfx] Contribute to DRM

[Lucas Tanure]

Hi,

I would like to start to contribute to drm part of kernel. I tried a few
things:

- Compiled linux-next tree using C=1 (sparse) to find things to improve.
But couldn't find any problem or issue.
- I looked in "www.x.org/wiki/DRMJanitors/" for stuff to do, but seems that
most of them are already done when I checked the code.

- Compiled and run the linux-next tree to test the code. And for this I got
the warning below.
I tried to compile a few older versions of linux-next in order to find the
offending commit. But I didn't succeed, many commits don't boot at all, and
is difficult to get more information about the status of the warning for
that version.

So, I would like some tips about how to debug DRM code, how to test, how to
get more information about issues.
What I do is :
- Compile and run
- Restart to a good kernel
- "journalctl --boot=-1"  to see if I got any warning on previous kernel

Also, if any developer needs/wants some help and it's ok to guide a new guy
in DRM code, I would like to get help about tasks to do, things to
clean/improve.
I'm reading https://www.kernel.org/doc/htmldocs/drm/ to start, and I have
done a few courses from linux foundation.

Thanks
Best Regards

--
Lucas Tanure
br.linkedin.com/in/lucastanure

WARNING: CPU: 3 PID: 243 at drivers/gpu/drm/drm_drv.c:569
drm_dev_alloc+0x251/0x320 [drm]()
Modules linked in: i915(+) joydev input_leds mousedev intel_rapl iosf_mbi
x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm ttm
hid_generic drm_kms_helper crct10dif_pclmul snd_hda_intel crc32_pclmul
usbhid snd_hda_codec crc32c_intel drm hid ghash_clmulni_intel snd_hda_core
eeepc_wmi asus_wmi aesni_intel iTCO_wdt sparse_keymap snd_hwdep led_class
aes_x86_64 lrw snd_pcm iTCO_vendor_support rfkill mxm_wmi evdev gf128mul
intel_gtt e1000e glue_helper mac_hid snd_timer syscopyarea ablk_helper
cryptd sysfillrect psmouse snd sysimgblt pcspkr fb_sys_fops ptp mei_me
i2c_i801 i2c_algo_bit soundcore mei shpchp i2c_core pps_core lpc_ich
serio_raw wmi fan battery processor thermal video button sch_fq_codel
ip_tables x_tables ext4 crc16 mbcache jbd2 sd_mod atkbd libps2 ahci libahci
libata
 xhci_pci xhci_hcd ehci_pci ehci_hcd scsi_mod usbcore usb_common i8042 serio
CPU: 3 PID: 243 Comm: systemd-udevd Not tainted 4.2.0-next-20150912-ARCH #5
Hardware name: System manufacturer System Product Name/Maximus IV GENE-Z,
BIOS 3603 11/09/2012
 0000000000000000 000000005ca47666 ffff88060f70b9d0 ffffffff812b9159
 0000000000000000 ffff88060f70ba08 ffffffff81074e62 ffff880612d39000
 ffffffffa06c7100 ffff880612f66098 ffffffffa06c7100 ffffffffa0691760
Call Trace:
 [<ffffffff812b9159>] dump_stack+0x4b/0x72
 [<ffffffff81074e62>] warn_slowpath_common+0x82/0xc0
 [<ffffffff81074faa>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa0422291>] drm_dev_alloc+0x251/0x320 [drm]
 [<ffffffffa0424d0b>] drm_get_pci_dev+0x3b/0x1e0 [drm]
 [<ffffffffa05dd2d4>] i915_pci_probe+0x34/0x50 [i915]
 [<ffffffff812fdec5>] local_pci_probe+0x45/0xa0
 [<ffffffff812fde10>] ? pci_match_device+0xe0/0x110
 [<ffffffff812ff053>] pci_device_probe+0x103/0x150
 [<ffffffff813d7942>] driver_probe_device+0x222/0x490
 [<ffffffff813d7c34>] __driver_attach+0x84/0x90
 [<ffffffff813d7bb0>] ? driver_probe_device+0x490/0x490
 [<ffffffff813d557c>] bus_for_each_dev+0x6c/0xc0
 [<ffffffff813d70fe>] driver_attach+0x1e/0x20
 [<ffffffff813d6c4b>] bus_add_driver+0x1eb/0x280
 [<ffffffff813d8540>] driver_register+0x60/0xe0
 [<ffffffff812fd73c>] __pci_register_driver+0x4c/0x50
 [<ffffffffa0424f90>] drm_pci_init+0xe0/0x110 [drm]
 [<ffffffffa06e6000>] ? 0xffffffffa06e6000
 [<ffffffffa06e60a4>] i915_init+0xa4/0xab [i915]
 [<ffffffff81002123>] do_one_initcall+0xb3/0x200
 [<ffffffff81199801>] ? __vunmap+0x91/0xe0
 [<ffffffff811589a0>] do_init_module+0x5f/0x1ef
 [<ffffffff810fa707>] load_module+0x2197/0x27e0
 [<ffffffff810f7550>] ? symbol_put_addr+0x50/0x50
 [<ffffffff81188695>] ? __pte_alloc_kernel+0xa5/0xf0
 [<ffffffff810fae9e>] SyS_init_module+0x14e/0x190
 [<ffffffff8157046e>] entry_SYSCALL_64_fastpath+0x12/0x71
---[ end trace d2652104b24a32ff ]---
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