linux-kernel - Re: [PATCH] of: Add of_get_memory

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Message-ID: <6a5a6cdc-e5e0-0f94-4eba-cfaaf0a16b19@gmail.com>
Date:   Thu, 17 Oct 2019 13:35:35 -0500
From:   Frank Rowand <frowand.list@...il.com>
To:     Rob Herring <robh@...nel.org>, rananta@...eaurora.org
Cc:     Trilok Soni <tsoni@...eaurora.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] of: Add of_get_memory_prop()

Hi Raghavendra,

I have not received your emails in this conversation, and I do not see
them in my spam folder.  I see some replies from Rob, so I am guessing
he added me to the CC: list.

Please add me to future Devicetree emails.

Digging a little deeper, in the devicetree mail list archive, I see
myself on the CC: list of your "Date: Wed, 18 Sep 2019 15:32:14 -0700"
reply to Rob.  I'm not sure why that email did not get through to me.

So just a heads up that something may be interfering with delivery of email
from you to me.  I've seen disappearing email problem from other senders,
even when most of their emails get through.

Thanks,

Frank


On 10/01/2019 17:09, Rob Herring wrote:
> On Wed, Sep 18, 2019 at 03:32:14PM -0700, rananta@...eaurora.org wrote:
>> On 2019-09-18 13:13, Rob Herring wrote:
>>> On Wed, Sep 18, 2019 at 1:47 PM Raghavendra Rao Ananta
>>> <rananta@...eaurora.org> wrote:
>>>>
>>>> On some embedded systems, the '/memory' dt-property gets updated
>>>> by the bootloader (for example, the DDR configuration) and then
>>>> gets passed onto the kernel. The device drivers may have to read
>>>> the properties at runtime to make decisions. Hence, add
>>>> of_get_memory_prop() for the device drivers to query the requested
>>>
>>> Function name doesn't match. Device drivers don't need to access the
>>> FDT.
>>>
>>>> properties.
>>>>
>>>> Signed-off-by: Raghavendra Rao Ananta <rananta@...eaurora.org>
>>>> ---
>>>>  drivers/of/fdt.c       | 27 +++++++++++++++++++++++++++
>>>>  include/linux/of_fdt.h |  1 +
>>>>  2 files changed, 28 insertions(+)
>>>
>>> We don't add kernel api's without users.
>>>
>>>>
>>>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>>>> index 223d617ecfe1..925cf2852433 100644
>>>> --- a/drivers/of/fdt.c
>>>> +++ b/drivers/of/fdt.c
>>>> @@ -79,6 +79,33 @@ void __init of_fdt_limit_memory(int limit)
>>>>         }
>>>>  }
>>>>
>>>> +/**
>>>> + * of_fdt_get_memory_prop - Return the requested property from the
>>>> /memory node
>>>> + *
>>>> + * On match, returns a non-zero positive value which represents the
>>>> property
>>>> + * value. Otherwise returns -ENOENT.
>>>> + */
>>>> +int of_fdt_get_memory_prop(const char *pname)
>>>> +{
>>>> +       int memory;
>>>> +       int len;
>>>> +       fdt32_t *prop = NULL;
>>>> +
>>>> +       if (!pname)
>>>> +               return -EINVAL;
>>>> +
>>>> +       memory = fdt_path_offset(initial_boot_params, "/memory");
>>>
>>> Memory nodes should have a unit-address, so this won't work frequently.
>> Sorry, can you please elaborate more on this? What do you mean by
>> unit-address and working frequently?
> 
> A memory node is typically going to be something like: /memory@...00000. 
> So your function will not work for any of those cases. And just 
> '/memory' generates a dtc warning.
> 
> Rob
> 
>