I went down the eeprom rabbithole a bit. To access and manipulate RPI4's eeprom directly, Plan 9 would need to support a device like /dev/vchiq (VideoCore interface) on Linux:
https://github.com/raspberrypi/linux/blob/rpi-3.2.27/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c#L334 The rest of the tools (e.g. rpi-eeprom-update) eventually use vcgencmd which ioctl into /dev/vchiq. My /dev/mmcblk comment was wrong. On Sat, Jan 16, 2021 at 2:15 PM Bakul Shah <ba...@iitbombay.org> wrote: > I believe all it takes is the presence of recover.bin file on the dos > partition. > You still need an updated eeprom image for it to flash the real eeprom with > but preparing this image doesn't require any h/w access. Unless things > have changed in the last year. > > On Jan 16, 2021, at 1:24 PM, Skip Tavakkolian <skip.tavakkol...@gmail.com> > wrote: > > regarding /dev/serial, this should be helpful for anyone wanting to set up > netboot. > > If you have a number of RPI's that netboot, the way that the common > config.txt is segmented for each board is by using the '[serial number in > hex]' section headers. Unfortunately, netboot also requires changing the > BOOT_ORDER parameter in EEPROM, which requires access to /dev/mmcblk* and > some way of generating the proper .bin format. So Linux is still needed for > the initial setup. > > On Sat, Jan 16, 2021 at 9:13 AM Richard Miller <9f...@hamnavoe.com> wrote: > >> > I didn't realise the 9pi image was not up to date. >> > I'll put a new one on 9p.io today. >> >> I've done that. Sorry for letting it get out of sync with the kernel >> source. >> >> The new contrib/miller/9pi.img.gz has >> - the latest firmware files from the raspberry pi github >> - the update to initialise xhci firmware for pi400 and recent pi4 boards >> - a tweak to the pi4 gigabit ethernet driver to allow jumbo packets >> - a new /dev/serial device from which you can read the board serial >> number (I forget why) >> >> Nothing outside the kernel has changed from the previous image. >> > > *9fans <https://9fans.topicbox.com/latest>* / 9fans / see discussions > <https://9fans.topicbox.com/groups/9fans> + participants > <https://9fans.topicbox.com/groups/9fans/members> + delivery options > <https://9fans.topicbox.com/groups/9fans/subscription> Permalink > <https://9fans.topicbox.com/groups/9fans/Tfcf12cca3a14dc8a-M4df905923fb217a0834ea1f0> > ------------------------------------------ 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/Tfcf12cca3a14dc8a-M9568b0b0d78c08e1ec367e5c Delivery options: https://9fans.topicbox.com/groups/9fans/subscription
