linux-kernel - Re: [RFC PATCH] mmc: dw_mmc: remove redundant num

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Message-id: <56A19811.9000101@samsung.com>
Date:	Fri, 22 Jan 2016 11:46:41 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Shawn Lin <shawn.lin@...k-chips.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mmc: dw_mmc: remove redundant num_slots check

Hi, Shawn.

On 01/21/2016 04:52 PM, Shawn Lin wrote:
> num_slots comes from pdata if existing, otherwise from
> dw_mci_parse_dt which make it at least one slot. If
> num_slots is less than 1 for the existing pdata case,
> current code return -ENODEV. But dw_mci_probe seems to
> treat this a optional case as it will call SDMMC_GET_SLOT_NUM
> if no slot assigned.

Well, we need to consider more thing..
Host can get the number of slot from SDMMC_GET_SLOT_NUM().
But i think this way also has the problem.

num_slot isn't defined anywhere, and num_slot should be set to value of SDMMC_GET_SLOT_NUM.
If that value is higher than 1, it should be blocking..(I didn't test all cases..)

Even though this patch is not correct, i could check the problem relevant to num_slot, because of this patch. :)

my suggestion is if pdata->num_slot is not defined anywhere, just set to 1 by default.
not take from SDMMC_GET_SLOT_NUM.

if (host->pdata->nums_slots < 1 || 
	host->pdata->nums_slots > SDMMC_GET_SLOT_NUM())

This is correct condition. num_slots can't be higher than number of supported slots.
how about?

Best Regards,
Jaehoon Chung

> 
> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
> 
> ---
> 
>  drivers/mmc/host/dw_mmc.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 7128351..a116ec6 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -2949,12 +2949,6 @@ int dw_mci_probe(struct dw_mci *host)
>  		}
>  	}
>  
> -	if (host->pdata->num_slots < 1) {
> -		dev_err(host->dev,
> -			"Platform data must supply num_slots.\n");
> -		return -ENODEV;
> -	}
> -
>  	host->biu_clk = devm_clk_get(host->dev, "biu");
>  	if (IS_ERR(host->biu_clk)) {
>  		dev_dbg(host->dev, "biu clock not available\n");
>