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Date:   Sat, 19 Feb 2022 13:42:55 +0300
From:   Ivan Bornyakov <i.bornyakov@metrotek.ru>
To:     Xu Yilun <yilun.xu@intel.com>
Cc:     mdf@kernel.org, hao.wu@intel.com, trix@redhat.com,
        conor.dooley@microchip.com, linux-kernel@vger.kernel.org,
        linux-fpga@vger.kernel.org, system@metrotek.ru
Subject: Re: [PATCH v4] fpga: microchip-spi: add Microchip FPGA manager
Message-ID: <20220219104255.smgqcqlez6sdo4hk@x260>
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 <20220218160555.GA1333893@yilunxu-OptiPlex-7050>
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On Sat, Feb 19, 2022 at 09:16:27AM +0300, Ivan Bornyakov wrote:
> On Sat, Feb 19, 2022 at 12:05:55AM +0800, Xu Yilun wrote:
> >
> > Maybe the bitstream info at the head of the image could be parsed in
> > write_init(), and this requires the driver fill the
> > fpga_manager_ops.initial_header_size
> >
> 
> Header size is not known beforehand and is stored in 25th byte of the
> image.
> 

Actually I was not quite accurate here. The header itself seems to be of
constant size according to
https://coredocs.s3.amazonaws.com/DirectC/2021_2/spi_directc.pdf
(4. Data File Format)

But the lookup table is definitely of a variable size. Moreover
bitstream start and size both are somewhere in the image and needed
to be located through lookup table.