linux-kernel - Re: [PATCH V0 1/1] bootconfig: Increase max size of bootconfig from 32 KB to 256 KB for DCC support

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Message-Id: <20230110001820.5ca81344286f614ed4ccec77@kernel.org>
Date:   Tue, 10 Jan 2023 00:18:20 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Souradeep Chowdhury <quic_schowdhu@...cinc.com>
Cc:     <linux-kernel@...r.kernel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>,
        Sai Prakash Ranjan <quic_saipraka@...cinc.com>,
        Sibi Sankar <quic_sibis@...cinc.com>,
        Rajendra Nayak <quic_rjendra@...cinc.com>
Subject: Re: [PATCH V0 1/1] bootconfig: Increase max size of bootconfig from
 32 KB to 256 KB for DCC support

On Mon, 9 Jan 2023 20:01:05 +0530
Souradeep Chowdhury <quic_schowdhu@...cinc.com> wrote:

> Increasing the memory size of bootconfig to be able to handle a max number of
> 8192 nodes to be fitted in memory size of 256KB.

Sorry, but you missed the 'xbc_node::data' stores the index of the data and
that is uint16_t. So the XBC_DATA_MAX is fixed limitation.

The number of nodes (XBC_NODE_MAX) can be expanded because I just decided it
to keep the pre-compiled array size ~8KB. Maybe expanding it to 64KB just
increase the size of kernel on init memory (and freed after boot).

Could you tell me why you need such a big data for your DCC?

Thank you,

> 
> Signed-off-by: Souradeep Chowdhury <quic_schowdhu@...cinc.com>
> ---
>  include/linux/bootconfig.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
> index 1611f9d..64d233b 100644
> --- a/include/linux/bootconfig.h
> +++ b/include/linux/bootconfig.h
> @@ -55,11 +55,11 @@ struct xbc_node {
>  } __attribute__ ((__packed__));
>  
>  #define XBC_KEY		0
> -#define XBC_VALUE	(1 << 15)
> -/* Maximum size of boot config is 32KB - 1 */
> +#define XBC_VALUE	(1 << 18)
> +/* Maximum size of boot config is 256KB - 1 */
>  #define XBC_DATA_MAX	(XBC_VALUE - 1)
>  
> -#define XBC_NODE_MAX	1024
> +#define XBC_NODE_MAX	8192
>  #define XBC_KEYLEN_MAX	256
>  #define XBC_DEPTH_MAX	16
>  
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>