----- Original Message ----- > From: "Martyn Welch" <martyn.welch@xxxxxx> > Subject: Re: [PATCH 1/3] vme_user: Ensure driver compiles after VME bridges > > On 05/11/13 17:53, Aaron Sierra wrote: > > Martyn, > > Can you please elaborate on why you feel it is not a fix? For instance, > > will this type of solution not be accepted upstream? Is this solution not > > complete enough? Do you feel that it doesn't resolve any issue? > > > > -Aaron > > The vme_user driver is in the staging tree as it is not in a fit state to > incorporate into the main kernel tree. As far as I can see, the below patch > just causes the driver to be built at a subtly different time, from a subtly > different location (outside of the staging tree). To be honest, I'm not sure > how this is fixing anything. > > Martyn Martyn, You are correct about the function of this patch, however, I know that it resolves a real problem despite its inconsequential appearance. Using a 3.10.6 kernel, if I compile vme, vme_tsi148, and vme_user as modules, then attempting to insert vme_user into the kernel before the vme subsystem driver has been loaded results in the module failing to load with the following (this is good): vme_user: Unknown symbol vme_master_read (err 0) vme_user: Unknown symbol vme_master_write (err 0) vme_user: Unknown symbol vme_free_consistent (err 0) vme_user: Unknown symbol vme_register_driver (err 0) vme_user: Unknown symbol vme_irq_generate (err 0) vme_user: Unknown symbol vme_alloc_consistent (err 0) vme_user: Unknown symbol vme_slave_request (err 0) vme_user: Unknown symbol vme_master_free (err 0) vme_user: Unknown symbol vme_master_request (err 0) vme_user: Unknown symbol vme_slave_free (err 0) vme_user: Unknown symbol vme_slave_set (err 0) vme_user: Unknown symbol vme_master_get (err 0) vme_user: Unknown symbol vme_slave_get (err 0) vme_user: Unknown symbol vme_master_set (err 0) vme_user: Unknown symbol vme_unregister_driver (err 0) vme_user: Unknown symbol vme_get_size (err 0) This "Unknown symbol" error forces modules to be loaded in this order at the very least; vme -> vme_user. However, when these modules are compiled into the kernel, unfortunate things start to take place. This is the order that the three VME drivers are compiled when using an unpatched kernel: CC drivers/staging/vme/devices/vme_user.o LD drivers/staging/vme/devices/built-in.o LD drivers/staging/vme/built-in.o LD drivers/staging/built-in.o CC drivers/vme/vme.o CC drivers/vme/bridges/vme_tsi148.o LD drivers/vme/bridges/built-in.o LD drivers/vme/built-in.o LD drivers/built-in.o Note that this is not only the order that the drivers are compiled, but also the order that they are initialized. Also notice that since all three drivers are compiled into the kernel, there are no "Unknown symbols" to prevent the vme_user driver from initializing as if the VME bus subsystem has already been initialized. Therefore the following load order occurs; vme_user -> vme -> vme_tsi148. This is the result of the unpatched initialization order: [snip] hidraw: raw HID events driver (C) Jiri Kosina usbcore: registered new interface driver usbhid usbhid: USB HID core driver vme_user: VME User Space Access Driver ------------[ cut here ]------------ kernel BUG at drivers/base/driver.c:169! invalid opcode: 0000 [#1] SMP Modules linked in: CPU: 1 PID: 1 Comm: swapper/0 Not tainted 3.10.6-xes_r3-00018-g300fcda-dirty #112 Hardware name: Extreme Engineering Solutions, Inc. (X-ES) XCalibur4331/XCalibur4331, BIOS 1-2.21.1 12/10/2012 task: ffff880232888000 ti: ffff880232884000 task.ti: ffff880232884000 RIP: 0010:[<ffffffff812ba23a>] [<ffffffff812ba23a>] driver_register+0x1d/0x106 RSP: 0000:ffff880232885e18 EFLAGS: 00010246 RAX: ffffffff8184ef20 RBX: ffffffff8184ee68 RCX: 0000000000000026 RDX: 0000000000000023 RSI: 0000000000000020 RDI: ffffffff8184ee68 RBP: ffff880232885e48 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: ffffffff81d5f420 R12: ffffffff8184ee30 R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff8184eee0 FS: 0000000000000000(0000) GS:ffff88023bc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000000 CR3: 000000000180c000 CR4: 00000000000007e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Stack: 0000000000000001 ffffffff818a576d ffffffff8184ee30 0000000000000000 0000000000000000 ffffffff8184eee0 ffff880232885eb8 ffffffff813a63aa ffff880232885eb8 ffffffff814bc12b ffff880232885eb8 0000002000000008 Call Trace: [<ffffffff818a576d>] ? staging_init+0x8/0x8 [<ffffffff813a63aa>] vme_register_driver+0x4c/0x23b [<ffffffff814bc12b>] ? printk+0x48/0x4a [<ffffffff818a576d>] ? staging_init+0x8/0x8 [<ffffffff818a5790>] vme_user_init+0x23/0x25 [<ffffffff81000243>] do_one_initcall+0x7b/0x10c [<ffffffff81880d5e>] kernel_init_freeable+0x101/0x190 [<ffffffff818806b0>] ? do_early_param+0x86/0x86 [<ffffffff814b7e4b>] ? rest_init+0x6f/0x6f usb 1-1: new high-speed USB device number 2 using ehci-pci [<ffffffff814b7e54>] kernel_init+0x9/0xd1 [<ffffffff814c276c>] ret_from_fork+0x7c/0xb0 [<ffffffff814b7e4b>] ? rest_init+0x6f/0x6f Code: 9e f0 ff 48 8b 83 90 00 00 00 5a 5b 5d c3 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 89 fb 41 50 48 8b 47 08 48 83 78 78 00 75 02 <0f> 0b 48 83 78 40 00 74 07 48 83 7f 38 00 75 1c 48 83 78 48 00 RIP [<ffffffff812ba23a>] driver_register+0x1d/0x106 RSP <ffff880232885e18> ---[ end trace 0ccf2d5a87725d2a ]--- Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b [snip] After applying the patch that I submitted, the three VME drivers are compiled as such: CC drivers/vme/vme.o CC drivers/vme/../staging/vme/devices/vme_user.o LD drivers/vme/../staging/vme/devices/built-in.o LD drivers/vme/../staging/vme/built-in.o CC drivers/vme/bridges/vme_tsi148.o LD drivers/vme/bridges/built-in.o LD drivers/vme/built-in.o You should see that this forces the vme_user driver to compile after the VME subsystem driver and therefore initialize in the necessary order (and without the kernel panic): [snip] hidraw: raw HID events driver (C) Jiri Kosina usbcore: registered new interface driver usbhid usbhid: USB HID core driver vme_tsi148 0000:04:04.0: Board is the VME system controller vme_tsi148 0000:04:04.0: VME geographical address is 1 vme_tsi148 0000:04:04.0: VME Write and flush and error check is disabled vme_tsi148 0000:04:04.0: CR/CSR Offset: 1 vme_tsi148 0000:04:04.0: Enabling CR/CSR space vme_user: VME User Space Access Driver [snip] Thanks for reconsidering. -Aaron _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
