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Message-ID: <81C3A93C17462B4BBD7E272753C1057923B924C92E@EXDCVYMBSTM005.EQ1STM.local> Date: Tue, 14 Aug 2012 19:06:51 +0200 From: Sjur BRENDELAND <sjur.brandeland@...ricsson.com> To: Ohad Ben-Cohen <ohad@...ery.com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Linus Walleij <linus.walleij@...aro.org>, Sjur Brændeland <sjurbren@...il.com> Subject: RE: [RFC 4/4] remoteproc: Add driver for STE Modem Hi Ohad, >>> It seems to me that a char device will solve these issues: we can use >>> ioctl to control the power, if the user crashes we'll know about it >>> via the release handler, and if the remote processor crashes we can >>> let the user know by sending it a notification for it to read via the fd. How about skipping definition of ioctls and simply call rproc_boot() upon open and rproc_shutdown() upon close, this is perhaps quirky, but simpler. I'd also like to use a char-misc device, then we get the device node with proper name automatically from existing udev rules. >> In this case we need a way to make the virtio-drivers release the >> virtio-queues in order to decrement the refcount, right? ... >> So it seems that we need to force an unregistration of the virtio devices, >> in order to make it release its queues. ... > Yeah, no code is needed; something like this should do the trick: > > root@...p4430-panda:/sys/bus/virtio/drivers/virtio_console# echo > virtio1 > unbind Looking on this once more after vacation I prefer if the ste-rproc driver could enforce shutdown if we use the char-device. In our case user-space will detect modem crashes and power off the device. So if user-space uses char-device to request power off, it feels like kernel space should do everything possible to really trigger the shutdown, including unbinding the virtio devices. Depending on additional "echo .../virtio > unbind" seems like an unnecessary extra dependency. Alternatively, we could let user-space handle the power switch for the modem directly. Remoteproc could simply notify user-space (e.g. using gen-netlink) when rproc usage count has dropped to zero. And this could trigger power-down. This would be more aligned with our existing solution for power control. Regards, Sjur -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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