Re: [PATCH 4/8] bus: mhi: Add inbound buffers allocation flag

From: Greg KH <gregkh@linuxfoundation.org>
To: Loic Poulain <loic.poulain@linaro.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	Hemant Kumar <hemantk@codeaurora.org>,
	Bhaumik Bhatt <bbhatt@codeaurora.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	Jakub Kicinski <kuba@kernel.org>
Subject: Re: [PATCH 4/8] bus: mhi: Add inbound buffers allocation flag
Date: Thu, 24 Jun 2021 18:48:15 +0200	[thread overview]
Message-ID: <YNS3T6Tp4oc66zFh@kroah.com> (raw)
In-Reply-To: <CAMZdPi9=F0agD=5eSmVngmDRXNhb7TstQzgMSXFoJzkuRVFtjQ@mail.gmail.com>

On Thu, Jun 24, 2021 at 05:39:58PM +0200, Loic Poulain wrote:
> Hi Greg,
> 
> On Thu, 24 Jun 2021 at 15:51, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Mon, Jun 21, 2021 at 09:46:12PM +0530, Manivannan Sadhasivam wrote:
> > > From: Loic Poulain <loic.poulain@linaro.org>
> > >
> > > Currently, the MHI controller driver defines which channels should
> > > have their inbound buffers allocated and queued. But ideally, this is
> > > something that should be decided by the MHI device driver instead,
> > > which actually deals with that buffers.
> > >
> > > Add a flag parameter to mhi_prepare_for_transfer allowing to specify
> > > if buffers have to be allocated and queued by the MHI stack.
> > >
> > > Keep auto_queue flag for now, but should be removed at some point.
> > >
> > > Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> > > Tested-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> > > Reviewed-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> > > Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
> > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > > Acked-by: Jakub Kicinski <kuba@kernel.org>
> > > Link: https://lore.kernel.org/r/1621603519-16773-1-git-send-email-loic.poulain@linaro.org
> > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> [...]
> > > +/**
> > > + * enum mhi_chan_flags - MHI channel flags
> > > + * @MHI_CH_INBOUND_ALLOC_BUFS: Automatically allocate and queue inbound buffers
> > > + */
> > > +enum mhi_chan_flags {
> > > +     MHI_CH_INBOUND_ALLOC_BUFS = BIT(0),
> >
> > Why is an enumerated type a bitfield?
> >
> > Please just use integers for enumerated types.
> 
> This 'trick' for listing flags is used in other places like drm,
> mac80211, etc...: grep -r "BIT(0)," ./include/

An enum is a list of values that are unique.  Not values you can mush
together into a single variable and look at the bit masks of.

> I don't understand why it would not be right? should we simply use
> a list of defines for this?

What are you using this for?  If you are going to combine them, then
yes, use #defines.

thanks,

greg k-h