Hi Chiawei, > Yes, there is security concern using HW mode. > Our designer is considering to remove the HW mode support in the next > generation of Aspeed SoCs. > So far we haven't encountered a scenario demanding HW mode. Great to hear :) can we unconditionally set ESPI000[9] in the driver then? > > With than in mind, if we're disabling hardware mode - what does the > > direction control setting effect when we're in software mode > > (ESPICTRL[9] == 1)? Does it even matter? > > Yes, the direction matters even in SW mode. > When the direction is 'master-to-slave' and the GPIO value is updated > by the Host through PUT_VW, a VW interrupt is trigger to notify BMC. > For the 'slave-to-master' GPIO, a alert is generated to notify the > Host to issue GET_VW for the GPIO value updated by the BMC by > ESPI09C. OK, but the datasheet mentions that ESPICFG804 is only applicable when ESPI000[9] = 0, or is that not the case? But based on what you've said: yes, it sounds like the generic gpiodev parts won't be useful for this. > > Separate from this: I'm also proposing that we represent the system > > event VWs > > as gpiodevs as well. > > > > > A raw packet, primitive interface should have better flexibility > > > to > > > manage MCTP packets over the OOB channel. > > > > OK, let me phrase this differently: can the OOB channel be used for > > anything other than SMBus messaging? Is it useful to provide an > > interface that isn't a standard SMBus/i2c device? > > Yes, the PCH spec. also defines two additional packet format for an > eSPI slave to retrieve PCH Temperature Data and RTC time. > It should be trivial to prepare a byte buffer in that format and send > it through the raw packet interface. OK, understood. > > If you need custom uapi definitions for this driver, that might be > > okay, but it's going to be more work for you (to define an interface > > that can be supported long-term), rather than using standard > > infrastructure that already exists. > > Thus I suggested that we can refer to the IPMI KCS BMC driver, which > supports the selection of different user interfaces, RAW or IPMI. Yep, but the KCS "raw" register set is standardised as part of the IPMI spec too, which helps to define a stable user API. We don't have that in this case. Overall though, if you want to start with the "low-level" API, then introduce "enhanced" functionality - like an actual SMBus driver - alongside that, then that sounds like an OK approach. > If IOCTL is considered to be not user friendly or magic code > polluting, file-based read/write on the miscdevice node is also an > option. It's not really my decision to make, but a read/write event interface would seem to be more consistent to me. Is there an obvious event format that would be common across all channels, perhaps? We'd probably also need a poll too - to make use of incoming events, like master-to-slave VW changes, perhaps? Cheers, Jeremy
