Re: PCI probing in the kernel
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Date: Sat, 26 Jun 2021 05:43:26 UTC
On Fri, Jun 25, 2021, 11:15 PM <saimabaig11@gmail.com> wrote: > It specifically says **em** probing and then it calls the **em_register** > function repeatedly which is the registration routine that the em driver > defines as part of its initialization. > The log you sent just shows em_register once. This is whats confusing me as to why is it repeatedly calling these > functions for a specific module repeatedly > It calls em probe 6 times, finds one and call em_register, then calls em probe 6 more times. Warner *From:* Warner Losh <imp@bsdimp.com> > *Sent:* Saturday, June 26, 2021 10:40 AM > *To:* saimabaig11@gmail.com > *Cc:* FreeBSD Hackers <freebsd-hackers@freebsd.org> > *Subject:* Re: PCI probing in the kernel > > > > > > > > On Fri, Jun 25, 2021 at 10:59 PM <saimabaig11@gmail.com> wrote: > > My question relates to how does the kernel go about its business of > discovering PCI devices (after boot time) . I am loading the e1000(em) > driver by kldloading the `if_em` module. The kernel seems to be calling the > probe routine multiple times. So the log below includes messages coming > from > the kernel and also includes my own debug logs. > > > > ``` > > Jun 25 11:16:45 FreeBSD12 kernel: em probing > > Jun 25 11:16:45 FreeBSD12 syslogd: last message repeated 5 times > > Jun 25 11:16:45 FreeBSD12 kernel: em0: +++ Calling em_register > > Jun 25 11:16:45 FreeBSD12 kernel: em probing > > Jun 25 11:16:45 FreeBSD12 syslogd: last message repeated 5 times > > Jun 25 11:16:45 FreeBSD12 kernel: em0: +++ Calling em_register > > Jun 25 11:16:45 FreeBSD12 kernel: em probing > > Jun 25 11:16:45 FreeBSD12 kernel: em0: +++ Calling em_register > > Jun 25 11:16:45 FreeBSD12 kernel: em0: <Intel(R) PRO/1000 Network > Connection> port 0x2000-0x203f mem > 0xfd5c0000-0xfd5dffff,0xfdff0000-0xfdffffff irq 19 at device 1.0 on pci2 > > Jun 25 11:16:45 FreeBSD12 kernel: em attaching > > Jun 25 11:16:45 FreeBSD12 kernel: em0: +++ Calling em_register > > Jun 25 11:17:34 FreeBSD12 kernel: em0: Using 2048 TX descriptors and 2048 > RX > descriptors > > Jun 25 11:17:35 FreeBSD12 kernel: em probing > > Jun 25 11:17:35 FreeBSD12 syslogd: last message repeated 5 times > > Jun 25 11:17:35 FreeBSD12 kernel: em1: +++ Calling em_register > > Jun 25 11:17:35 FreeBSD12 kernel: em probing > > Jun 25 11:17:36 FreeBSD12 kernel: Base = 5ee7e000, Length = 8000 > > ``` > > It seems that the `probe->register` sequence seems to be getting repeated > multiple times until the adapter is identified properly and its resources > allocated. Isn't multiple registration a cause of concern? Or may something > is wrong with the way I think. May be I am not getting it right? Could > someone elaborate? > > > > When you load a driver, we call probe on all the devices on the bus that > don't > > yet have drivers. I believe you are seeing this. The probe routine tries a > bunch > > of different devices until finding the NIC that doesn't have a driver. > It's completely > > normal and ordinary. > > > > Warner >