linux-kernel - Re: [RFC PATCH v2 0/1] FPGA subsystem core

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Message-ID: <524EDE5C.4040902@monstr.eu>
Date:	Fri, 04 Oct 2013 17:27:24 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Alan Tull <atull@...era.com>
CC:	Michal Simek <michal.simek@...inx.com>,
	linux-kernel@...r.kernel.org, Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dinh Nguyen <dinguyen@...era.com>,
	Philip Balister <philip@...ister.org>,
	Alessandro Rubini <rubini@...dd.com>,
	Steffen Trumtrar <s.trumtrar@...gutronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Jason Cooper <jason@...edaemon.net>,
	Yves Vandervennet <rocket.yvanderv@...il.com>,
	Kyle Teske <kyle.teske@...com>,
	Josh Cartwright <joshc@....teric.us>,
	Nicolas Pitre <nico@...aro.org>,
	Mark Langsdorf <mark.langsdorf@...xeda.com>,
	Felipe Balbi <balbi@...com>, linux-doc@...r.kernel.org,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	David Brown <davidb@...eaurora.org>,
	Rob Landley <rob@...dley.net>,
	"David S. Miller" <davem@...emloft.net>,
	Joe Perches <joe@...ches.com>,
	Cesar Eduardo Barros <cesarb@...arb.net>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH v2 0/1] FPGA subsystem core

Hi,

On 10/03/2013 11:46 PM, Alan Tull wrote:
> On Wed, 2013-10-02 at 17:35 +0200, Michal Simek wrote:
> 
>>
>> Through firmware interface:
>> cat /sys/class/fpga_manager/fpga0/name
>> echo -n fpga.bin > /sys/class/fpga_manager/fpga0/firmware
>>
>> Through sysfs bin file:
>> cat /sys/class/fpga_manager/fpga0/fpga_config_state
>> echo -n write_init > /sys/class/fpga_manager/fpga0/fpga_config_state
>> cat /lib/firmware/fpga.bin > /sys/class/fpga_manager/fpga0/fpga_config_data
>> echo -n write_complete > /sys/class/fpga_manager/fpga0/fpga_config_state
>>
> 
> Hi Michal,
> 
> I have v2 working for me with Altera socfpga and had some feedback.
> 
> Add me and Dinh as maintainers.

why not just one? What about you?

> 
> This driver now has two interfaces for programming the image.
> I don't think things in the kernel usually have multiple interfaces.

The question here is if this is a problem. i2c create char devices
and also provide sysfs access too. It is done through notification.

> Does the fpga community in general find that the firmware class is
> suitable for all our use cases?  I think it only supports the most simple
> use cases.

Let's continue with this on that second thread and we will see what happen.


> My original fpga framework that you started with supported writing the
> fpga device through the devnode, i.e.
> cat fpga.bin > /dev/fpga0
> I think we should get back to that basic char driver interface like that.
> It seems like if you have a char driver, you would open and write to the
> devnode instead of adding an attribute under /sys.

It is the same as above. As you know we can simple add support for char
device with the current set of functions without changing logic in the driver.

> 
> The 'flags' implementation is a nice way to do some locking.  But it doesn't
> replace the status op to get fpga manager status which vanished in v2.
> So please add that back.  Its interface was that catting the 'status'
> attribute got a status description from the low level driver such as
> 'power up phase' or 'reset phase'.  Too useful to just get rid of.

No problem to add it back but it means that core will loose control
about values which can be returned back to the user. It is probably better
to create set of return values.

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform



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