Home/ Questions/Q 926041
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-15T19:37:08+00:00

I just wrote a RTC driver for an NXP RTC chip on my board,

  • 0

I just wrote a RTC driver for an NXP RTC chip on my board, it works great. This chip also has some battery backed RAM that I’d like to make available to a user space application. The RTC framework doesn’t support this. It’s only 512 bytes but I’m tossed between doing a seekable CHAR driver or a full blown BLOCK driver. I’ve never done a block driver before but it appears to require a bit more information than a simple CHAR.

I could also interface with IOCTLS but that doesn’t feel as clean as it could be. What feels like the best way to make these bytes available to userland?

[EDIT] I forgot to mention that that the RTC chip is hanging off an I2C port, it’s not mapped into memory, thus not making it a good candidate for mmaping. [/EDIT]

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Block drivers are only for devices that look like disk drives. Are you going to put a filesystem on your 512 bytes? No? Make it a character device.

    You could just do it like other drivers have. Check out drivers/char/nvram.c. That creates a char device you can open(), read(), write(), lseek(), and close().

    • 0