From: Greg KH <gregkh@linuxfoundation.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Jeffrey Hugo <jhugo@codeaurora.org>,
arnd@arndb.de, smohanad@codeaurora.org, kvalo@codeaurora.org,
bjorn.andersson@linaro.org, hemantk@codeaurora.org,
linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 05/16] bus: mhi: core: Add support for ringing channel/event ring doorbells
Date: Mon, 27 Jan 2020 08:21:27 +0100 [thread overview]
Message-ID: <20200127072127.GA281402@kroah.com> (raw)
In-Reply-To: <20200127071052.GB4768@mani>
On Mon, Jan 27, 2020 at 12:40:52PM +0530, Manivannan Sadhasivam wrote:
> On Sat, Jan 25, 2020 at 02:46:31PM +0100, Greg KH wrote:
> > On Fri, Jan 24, 2020 at 03:51:12PM -0700, Jeffrey Hugo wrote:
> > > > +struct mhi_event_ctxt {
> > > > + u32 reserved : 8;
> > > > + u32 intmodc : 8;
> > > > + u32 intmodt : 16;
> > > > + u32 ertype;
> > > > + u32 msivec;
> > > > +
> > > > + u64 rbase __packed __aligned(4);
> > > > + u64 rlen __packed __aligned(4);
> > > > + u64 rp __packed __aligned(4);
> > > > + u64 wp __packed __aligned(4);
> > > > +};
> > >
> > > This is the struct that is shared with the device, correct? Surely it needs
> > > to be packed then? Seems like you'd expect some padding between msivec and
> > > rbase on a 64-bit system otherwise, which is probably not intended.
> > >
> > > Also I strongly dislike bitfields in structures which are shared with
> > > another system since the C specification doesn't define how they are
> > > implemented, therefore you can run into issues where different compilers
> > > decide to implement the actual backing memory differently. I know its less
> > > convinent, but I would prefer the use of bitmasks for these fields.
> >
> > You have to use bitmasks in order for all endian cpus to work properly
> > here, so that needs to be fixed.
> >
>
> Okay.
>
> > Oh, and if these values are in hardware, then the correct types also
> > need to be used (i.e. __u32 and __u64).
> >
>
> I thought the __* prefix types are only for sharing with userspace...
> Could you please clarify why it is needed here?
It crosses the kernel boundry, so it needs to use those types. This is
not a new requirement, has been there for decades.
greg k-h
next prev parent reply other threads:[~2020-01-27 7:21 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 11:18 [PATCH 00/16] Add MHI bus support Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 01/16] docs: Add documentation for MHI bus Manivannan Sadhasivam
2020-01-23 12:58 ` Arnd Bergmann
2020-01-23 13:10 ` Manivannan Sadhasivam
2020-01-23 13:19 ` Arnd Bergmann
2020-01-23 13:30 ` Manivannan Sadhasivam
2020-01-23 14:52 ` Jeffrey Hugo
2020-01-23 16:41 ` Jeffrey Hugo
2020-01-27 12:02 ` Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 02/16] bus: mhi: core: Add support for registering MHI controllers Manivannan Sadhasivam
2020-01-23 11:33 ` Greg KH
2020-01-23 11:56 ` Manivannan Sadhasivam
2020-01-23 17:05 ` Jeffrey Hugo
2020-01-23 18:14 ` Greg KH
2020-01-26 23:58 ` Jeffrey Hugo
2020-01-28 7:19 ` Manivannan Sadhasivam
2020-01-27 11:56 ` Manivannan Sadhasivam
2020-01-27 14:52 ` Jeffrey Hugo
2020-01-28 6:37 ` Manivannan Sadhasivam
2020-01-28 7:24 ` Greg KH
2020-01-28 7:27 ` Manivannan Sadhasivam
2020-01-24 8:29 ` Greg KH
2020-01-24 14:24 ` Jeffrey Hugo
2020-01-24 17:47 ` Greg KH
2020-01-24 18:12 ` Jeffrey Hugo
2020-01-25 13:26 ` Greg KH
2020-01-26 21:00 ` Jeffrey Hugo
2020-01-27 7:02 ` Manivannan Sadhasivam
2020-01-27 7:11 ` Greg KH
2020-01-23 11:18 ` [PATCH 03/16] bus: mhi: core: Add support for registering MHI client drivers Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 04/16] bus: mhi: core: Add support for creating and destroying MHI devices Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 05/16] bus: mhi: core: Add support for ringing channel/event ring doorbells Manivannan Sadhasivam
2020-01-23 11:39 ` Arnd Bergmann
2020-01-23 12:00 ` Manivannan Sadhasivam
2020-01-23 12:44 ` Arnd Bergmann
2020-01-23 13:01 ` Manivannan Sadhasivam
2020-01-23 14:44 ` Jeffrey Hugo
2020-01-24 22:51 ` Jeffrey Hugo
2020-01-25 13:46 ` Greg KH
2020-01-27 7:10 ` Manivannan Sadhasivam
2020-01-27 7:21 ` Greg KH [this message]
2020-01-23 11:18 ` [PATCH 06/16] bus: mhi: core: Add support for PM state transitions Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 07/16] bus: mhi: core: Add support for basic PM operations Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 08/16] bus: mhi: core: Add support for downloading firmware over BHIe Manivannan Sadhasivam
2020-01-28 19:36 ` Jeffrey Hugo
2020-01-29 6:56 ` Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 09/16] bus: mhi: core: Add support for downloading RDDM image during panic Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 10/16] bus: mhi: core: Add support for processing events from client device Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 11/16] bus: mhi: core: Add support for data transfer Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 12/16] bus: mhi: core: Add uevent support for module autoloading Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 13/16] MAINTAINERS: Add entry for MHI bus Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 14/16] net: qrtr: Add MHI transport layer Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 15/16] net: qrtr: Do not depend on ARCH_QCOM Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 16/16] soc: qcom: Do not depend on ARCH_QCOM for QMI helpers Manivannan Sadhasivam
2020-01-23 11:45 ` Arnd Bergmann
2020-01-23 12:03 ` Manivannan Sadhasivam
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