Re: [PATCH] eeprom: at24: Support custom device names for AT24 EEPROMs

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On Mon, Jun 07, 2021 at 03:31:55PM +0200, Bartosz Golaszewski wrote:
> On Mon, Jun 7, 2021 at 1:09 PM Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> >
> >
> > On 04/06/2021 11:00, Bartosz Golaszewski wrote:
> > > On Wed, Jun 2, 2021 at 7:08 PM Alexander Fomichev <fomichev.ru@xxxxxxxxx> wrote:
> >
> > ...
> >
> > >> This change has a serious defect, as it doesn't guarantee a name
> > >> uniqueness. For my case there are a bunch of NVMEM devices with
> > >> 'dimm-spd' name. So the module initialization fails with several error
> > >> dumps in dmesg, like following:
> > >>
> > >> [    4.784679] at24 3-0051: supply vcc not found, using dummy regulator
> > >> [    4.784781] sysfs: cannot create duplicate filename '/bus/nvmem/devices/dimm-spd'
> > >> [    4.784783] CPU: 24 PID: 1354 Comm: systemd-udevd Not tainted 5.13.0-rc4-at24-catch+ #25
> > >> [    4.784787] Call Trace:
> > >> [    4.784789] [c00000003f3eb010] [c000000000914700] dump_stack+0xc4/0x114 (unreliable)
> > >> [    4.784797] [c00000003f3eb060] [c00000000061c5c8] sysfs_warn_dup+0x88/0xc0
> > >> [    4.784803] [c00000003f3eb0e0] [c00000000061ccec] sysfs_do_create_link_sd+0x17c/0x190
> > >> [    4.784809] [c00000003f3eb130] [c000000000ac3014] bus_add_device+0x94/0x1d0
> > >> [    4.784817] [c00000003f3eb1b0] [c000000000abe7b8] device_add+0x428/0xb90
> > >> [    4.784822] [c00000003f3eb2a0] [c000000000debbd0] nvmem_register+0x220/0xe00
> > >> [    4.784829] [c00000003f3eb390] [c000000000dec80c] devm_nvmem_register+0x5c/0xc0
> > >> [    4.784835] [c00000003f3eb3d0] [c008000016f40c20] at24_probe+0x668/0x940 [at24]
> > >> [    4.784845] [c00000003f3eb650] [c000000000cfecd4] i2c_device_probe+0x194/0x650
> > >> [    4.784850] [c00000003f3eb6f0] [c000000000ac4d3c] really_probe+0x1cc/0x790
> > >> [    4.784855] [c00000003f3eb790] [c000000000ac545c] driver_probe_device+0x15c/0x200
> > >> [    4.784861] [c00000003f3eb810] [c000000000ac5ecc] device_driver_attach+0x11c/0x130
> > >> [    4.784866] [c00000003f3eb850] [c000000000ac5fd0] __driver_attach+0xf0/0x200
> > >> [    4.784873] [c00000003f3eb8d0] [c000000000ac1158] bus_for_each_dev+0xa8/0x130
> > >> [    4.784879] [c00000003f3eb930] [c000000000ac4104] driver_attach+0x34/0x50
> > >> [    4.784885] [c00000003f3eb950] [c000000000ac35f0] bus_add_driver+0x1b0/0x2f0
> > >> [    4.784893] [c00000003f3eb9e0] [c000000000ac70b4] driver_register+0xb4/0x1c0
> > >> [    4.784900] [c00000003f3eba50] [c000000000cfe498] i2c_register_driver+0x78/0x120
> > >> [    4.784905] [c00000003f3ebad0] [c008000016f41260] at24_init+0x6c/0x88 [at24]
> > >> [    4.784914] [c00000003f3ebb30] [c0000000000122c0] do_one_initcall+0x60/0x2c0
> > >> [    4.784920] [c00000003f3ebc00] [c0000000002537bc] do_init_module+0x7c/0x350
> > >> [    4.784926] [c00000003f3ebc90] [c000000000257904] __do_sys_finit_module+0xd4/0x160
> > >> [    4.784932] [c00000003f3ebdb0] [c00000000002c104] system_call_exception+0xf4/0x200
> > >> [    4.784938] [c00000003f3ebe10] [c00000000000cf70] system_call_vectored_common+0xf0/0x268
> > >> [    4.784944] --- interrupt: 3000 at 0x7c1adac4b4c4
> > >> [    4.784948] NIP:  00007c1adac4b4c4 LR: 0000000000000000 CTR: 0000000000000000
> > >> [    4.784951] REGS: c00000003f3ebe80 TRAP: 3000   Not tainted  (5.13.0-rc4-at24-catch+)
> > >> [    4.784955] MSR:  900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE>  CR: 48222844  XER: 00000000
> > >> [    4.784976] IRQMASK: 0
> > >>                GPR00: 0000000000000161 00007fffefc78b90 00007c1adad37000 0000000000000006
> > >>                GPR04: 00000f6614d56be0 0000000000000000 0000000000000006 0000000000000000
> > >>                GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> > >>                GPR12: 0000000000000000 00007c1adafde680 0000000020000000 0000000000000000
> > >>                GPR16: 0000000000000000 00000f66118b1980 00000f66118b1a18 00000f66118b1948
> > >>                GPR20: 0000000000000000 00000f6614d60500 00007fffefc78df0 00000f6614d535c0
> > >>                GPR24: 00000f6614d56be0 00000f6614d60500 000000000000000c 00000f6614d49cb0
> > >>                GPR28: 00000f6614d56be0 0000000000020000 0000000000000000 00000f6614d60500
> > >> [    4.785033] NIP [00007c1adac4b4c4] 0x7c1adac4b4c4
> > >> [    4.785036] LR [0000000000000000] 0x0
> > >> [    4.785040] --- interrupt: 3000
> > >> [    4.785146] at24: probe of 3-0051 failed with error -17
> > >>
> > >>
> > >> It needs either to use NVMEM_DEVID_AUTO flag irrespective of the 'label'
> > >> property or to add a sort of counter suffix to the name field.
> > >>
> > >>
> > >> Reported-by: Alexander Fomichev <fomichev.ru@xxxxxxxxx>
> > >> CC: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> > >>
> > >> --
> > >> Regards,
> > >>   Alexander
> > >
> > > Alexander: Thanks for your bug report. The counter suffix you suggest
> > > is precisely what NVMEM_DEVID_AUTO would do so I think we'll need to
> > > use it. On the other hand, a non-unique label is bad design but
> > > obviously we can't break working setups.
> >
> > Yes the intention was that the label itself would be unique. In our case
> > we wanted to have something specifically named 'system' or 'module' to
> > identify a specific eeprom.
> >
> > BTW I did a quick grep from 'dimm-spd' and did not find it in the
> > kernel. Where is the device-tree you are using?
> >
> > > Jon: As the author of this patch - do you have any objections/better ideas?
> >
> > I would need to check if appending a suffix then has ramifications for
> > what we were trying to achieve.
> >
> > Jon
> >
> > --
> > nvpublic
> 
> One alternative would be to use the label "as is" for the first device
> and then append ".x" for each subsequent device with a repeating
> label. Does this make sense?
> 

This was my second suggestion, which I called 'counter suffix'. But it
requires additional effort.

-- 
Regards,
  Alexander



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