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Re: [Qemu-devel] [PATCH v1 2/3] memory: Add sysbus memory device

From: Andreas Färber
Subject: Re: [Qemu-devel] [PATCH v1 2/3] memory: Add sysbus memory device
Date: Fri, 16 May 2014 17:22:59 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0


Am 15.04.2014 04:21, schrieb Peter Crosthwaite:
> Add a sysbus device consisting of a single ram. This allows for
> instantiation of RAM just like any other device. There are a number
> of good reasons to want to do this this:
> 1: Consistency. RAM is not that special where board level files should
> have to instantiate it with a completely different API. This reduces
> complexity of board level development by hiding the memory API
> completely and handling everything via the sysbus API.
> 2: Device tree completeness. Ram Now shows up in info-qtree and
> friends. E.g. Info qtree gives meaningful information under the
> root system bus:
>   dev: sysbus-memory, id "zynq.ocm_ram"
>     size = 262144 (0x40000)
>     read-only = false
>     irq 0
>     mmio 00000000fffc0000/0000000000040000
>   dev: sysbus-memory, id "zynq.ext_ram"
>     size = 134217728 (0x8000000)
>     read-only = false
>     irq 0
>     mmio 0000000000000000/0000000008000000

I had warned that I would nack any patch that justifies changes with
"info qtree", so here's your gentle NAK.

Please help deciding on the following patches, which do show such
devices the QOM way:


Note that this doesn't mean we can't create new SysBusDevices, it means
the commit message should be changed.


> 3: Remove dependence of global state. Board files don't have to
> explicity request the global singleton (and much unloved)
> address_space_memory() and go hacking on it. address_space_memory()
> is still ultimately used, but the ugliness is hidden in one place - the
> sysbus core (we can fix that another day).
> 4: Data driven machine creation. There is list discussion on being able
> to create or append-to sysbus machines in a data-driven way (whether
> thats from command-line, monitor or scripts or whatever). This patch
> removes the memory special case from that problem and allows RAM
> instantiation to come via whatever solutions we come up with sysbus
> device instantiation.
> Signed-off-by: Peter Crosthwaite <address@hidden>
> ---
>  hw/core/Makefile.objs   |  1 +
>  hw/core/sysbus-memory.c | 63 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 64 insertions(+)
>  create mode 100644 hw/core/sysbus-memory.c

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