Hi all,
I am writing a AC97 ASoC driver for the MPC5121e SoC from Freescale. This SoC has almost the same PSC (Programmable Serial Controllers) as the MPC5200B, for which there already is an AC97 driver: sound/soc/fsl/mpc5200-ac97.c, so I'd like to extend that one to also support the MPC5121e. This driver is supposed to work together with a second part, implementing the actual PCM driver: sound/soc/fsl/mpc5200_dma.c. Both drivers register themselves via platform_driver_register() in a regular module init function. The problem is, they do share the same driver data struct! So psc_ac97_of_probe() starts off calling
psc_dma = dev_get_drvdata(&op->dev);
right ahead and accessing it without checking. The DMA part of the driver does indeed create this struct psc_dma and calls dev_set_drvdata() on it at the end of the probe function. So obviously, it is supposed that the DMA driver somehow gets probed before the PSC driver, but I can't see where this is enforced. AFAIK, the order is fairly random, so it could be the other way around.... and indeed, in my case it is. Unfortunately I don't have MPC5200 hardware with AC97 to test this out, but only a MPC5121e based board. If I mimic this on the MPC5121e, it won't work, because the PSC driver gets probed first and obviously crashes with a NULL-pointer dereference in the next line of code!
If this is supposed to be broken, I'd like to fix it of course, but:
1.- I can't test it on a MPC5200B, so therefor I need help. 2.- Simply turning the dev_get/set_drvdata and chip initialization order around does work in my case, but doesn't seem a robust solution to me. Any idea how this should be handled?
Best regards,