linux-kernel - Re: [PATCH v2 1/1] OMAP4: DSS: Add panel for Blaze Tablet boards

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 18 Feb 2013 16:33:06 +0200
From:	Ruslan Bilovol <ruslan.bilovol@...com>
To:	Andi Shyti <andi.shyti@...il.com>
Cc:	Andi Shyti <andi@...zian.org>, tomi.valkeinen@...com,
	FlorianSchandinat@....de, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH v2 1/1] OMAP4: DSS: Add panel for Blaze Tablet boards

Hi Andy,

On Sun, Feb 17, 2013 at 4:17 PM, Andi Shyti <andi.shyti@...il.com> wrote:
>> >> +     char name[30];
>> >> +     char buf[50];
>> >> +
>> >> +     if (size >= sizeof(buf))
>> >> +             size = sizeof(buf);
>> >
>> > what's the point of this?
>>
>> This is a way to limit copied from userspace data by available buffer size,
>> widely used in current kernel sources. Are you implying there is some
>> better (more graceful) way?
>
> No indeed :)
> There is no other way, sorry for polluting the review :)
>
>> >> +     if ((pins[2] & 1) || (pins[3] & 1)) {
>> >> +             lanes |= (1 << 1);
>> >> +             ret |= tc358765_write_register(dssdev, PPI_D0S_CLRSIPOCOUNT,
>> >> +                                                     board_data->clrsipo);
>> >> +     }
>> >> +     if ((pins[4] & 1) || (pins[5] & 1)) {
>> >> +             lanes |= (1 << 2);
>> >> +             ret |= tc358765_write_register(dssdev, PPI_D1S_CLRSIPOCOUNT,
>> >> +                                                     board_data->clrsipo);
>> >> +     }
>> >> +     if ((pins[6] & 1) || (pins[7] & 1)) {
>> >> +             lanes |= (1 << 3);
>> >> +             ret |= tc358765_write_register(dssdev, PPI_D2S_CLRSIPOCOUNT,
>> >> +                                                     board_data->clrsipo);
>> >> +     }
>> >> +     if ((pins[8] & 1) || (pins[9] & 1)) {
>> >> +             lanes |= (1 << 4);
>> >> +             ret |= tc358765_write_register(dssdev, PPI_D3S_CLRSIPOCOUNT,
>> >> +                                                     board_data->clrsipo);
>> >> +     }
>> >
>> > Can't this be done in one single multiwrighting command since
>> > this registers are consecutive?
>> >
>> > You build once the array to write and you send it at once.
>>
>> In this particular case I disagree. Yes, it will be a little bit
>> faster, however:
>> 1) we write this for panel initialization only (so no impact in other cases)
>> 2) multiwriting of array will make code reading more difficult
>>
>> So I would like to leave it as-is
>> Same is for next your similar comment.
>
> If the hw is providing us some ways for simplifying the code I
> would use it. In this case we are talking about the i2c feature
> of multiwriting and multireading.
>
> Let's assume that we want to write on 8 different consecutive
> registers. In my opinion this aproach is quite "heavy":
>
>   uX register;
>
>   register = value1;
>   i2c_write(REG1, register);
>
>   register = value2;
>   i2c_write(REG2, register);
>
>   ...
>
> Usually what I do is this:
>
>   uX register[8];
>
>   for (i = 0; i < 8; i++)
>     register |= valuei << i; (or register[i] = valuei or whatever)
>
>   i2c_multi_write(REG, register, 8);
>
> of course this is a simplified example in pseudocode. I think
> it's more readable and we are making a better use of the i2c
> protocol.
>
> In your case you have some if statement that are making the multi
> writing more difficult, but still is not impossible.
>
> At the end it's still a matter of taste, so that you are free to
> choose whatever you prefer :)

Thank you for reviewing this.
Unfortunately, this driver is not accepted due to future OMAP DSS rework.

I will take into account your comments when will reimplement it for new
DSS architecture.

Thanks and best regards,
Ruslan

>
> Andi
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/