On Wed, Oct 01, 2014 at 11:44:59AM -0700, Danielle Costantino wrote: > Re-sending Proposal: > > Currently I2C mux devices that support multiple master arbitration are > the i2c-mux-pca9541 and i2c-arb-gpio-challenge drivers. I propose to > add the ability to configure an interrupt pin from the Master Selector > device to indicate that bus ownership has been lost. Once the device > loses ownership, all of its children should enter a pm sleep mode (as > you can't talk to them at this point) until master-ship has been > reacquired. > Not sure I understand what you are proposing here. A typical use case would be a power supply such as the one supported by drivers/hwmon/lineage-pem.c from both an active and standby system controller. The power supply needs to be accessible from both controllers. If one controller looses access, it can only mean that it did not follow the access protocol. Similar, one controller enforcing access means that it either does not follow the access protocol either, or that the other end did not follow the protocol (or maybe the other end died). In all cases, loss of access does not mean that the end device can or should be put in sleep mode, not even logically. All it means is that there was an access protocol error. Not sure if there is anything that can be done about that, but putting the device into sleep mode does not seem to be an appropriate response to me. > This has come up as an issue when the master loses control over a bus > the return code of all transactions to its lave devices is EIO (not > very helpful). > But, again, doesn't that mean that there was some access protocol error ? Shouldn't it try to re-acquire mastership instead, and block all accesses to slaves until it acquired it ? Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
