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    SubjectRe: [PATCH v2 02/16] bus: mhi: core: Add support for registering MHI controllers
    Hi Greg,

    On Thu, Feb 13, 2020 at 07:34:18AM -0800, Greg KH wrote:
    > On Thu, Feb 13, 2020 at 08:50:13PM +0530, Manivannan Sadhasivam wrote:
    > > On Tue, Feb 11, 2020 at 11:20:55AM -0800, Greg KH wrote:
    > > > On Wed, Feb 12, 2020 at 12:11:30AM +0530, Manivannan Sadhasivam wrote:
    > > > > Hi Greg,
    > > > >
    > > > > On Thu, Feb 06, 2020 at 05:57:55PM +0100, Greg KH wrote:
    > > > > > On Fri, Jan 31, 2020 at 07:19:55PM +0530, Manivannan Sadhasivam wrote:
    > > > > > > --- /dev/null
    > > > > > > +++ b/drivers/bus/mhi/core/init.c
    > > > > > > @@ -0,0 +1,407 @@
    > > > > > > +// SPDX-License-Identifier: GPL-2.0
    > > > > > > +/*
    > > > > > > + * Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.
    > > > > > > + *
    > > > > > > + */
    > > > > > > +
    > > > > > > +#define dev_fmt(fmt) "MHI: " fmt
    > > > > >
    > > > > > This should not be needed, right? The bus/device name should give you
    > > > > > all you need here from what I can tell. So why is this needed?
    > > > > >
    > > > >
    > > > > The log will have only the device name as like PCI-E. But that won't specify
    > > > > where the error is coming from. Having "MHI" prefix helps the users to
    > > > > quickly identify that the error is coming from MHI stack.
    > > >
    > > > If the driver binds properly to the device, the name of the driver will
    > > > be there in the message, so I suggest using that please.
    > > >
    > > > No need for this prefix...
    > > >
    > >
    > > So the driver name will be in the log but that won't help identifying where
    > > the log is coming from. This is more important for MHI since it reuses the
    > > `struct device` of the transport device like PCI-E. For instance, below is
    > > the log without MHI prefix:
    > >
    > > [ 47.355582] ath11k_pci 0000:01:00.0: Requested to power on
    > > [ 47.355724] ath11k_pci 0000:01:00.0: Power on setup success
    > >
    > > As you can see, this gives the assumption that the log is coming from the
    > > ath11k_pci driver. But the reality is, it is coming from MHI bus.
    >
    > Then you should NOT be trying to "reuse" a struct device.
    >
    > > With the prefix added, we will get below:
    > >
    > > [ 47.355582] ath11k_pci 0000:01:00.0: MHI: Requested to power on
    > > [ 47.355724] ath11k_pci 0000:01:00.0: MHI: Power on setup success
    > >
    > > IMO, the prefix will give users a clear idea of logs and that will be very
    > > useful for debugging.
    > >
    > > Hope this clarifies.
    >
    > Don't try to reuse struct devices, if you are a bus, have your own
    > devices as that's the correct way to do things.
    >

    I assumed that the buses relying on a different physical interface for the
    actual communication can reuse the `struct device`. I can see that the MOXTET
    bus driver already doing it. It reuses the `struct device` of SPI.

    And this assumption has deep rooted in MHI bus design.

    Thanks,
    Mani

    > thanks,
    >
    > greg k-h

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