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From: "Michał Pecio" <michal.pecio@gmail.com>
To: Niklas Neronin <niklas.neronin@linux.intel.com>
Cc: mathias.nyman@linux.intel.com, linux-usb@vger.kernel.org
Subject: Re: [PATCH v3 1/2] usb: xhci: correct debug message page size calculation
Date: Wed, 5 Mar 2025 09:32:48 +0100	[thread overview]
Message-ID: <20250305093248.3cc6c066@foxbook> (raw)
In-Reply-To: <20250204124145.3998098-2-niklas.neronin@linux.intel.com>

On Tue,  4 Feb 2025 14:41:43 +0200, Niklas Neronin wrote:
> The ffs() function returns the index of the first set bit, starting
> from 1. If no bits are set, it returns zero. This behavior causes an
> off-by-one page size in the debug message, as the page size
> calculation [1] is zero-based, while ffs() is one-based.
> 
> Fix this by subtracting one from the result of ffs(). Note that since
> variable 'val' is unsigned, subtracting one from zero will result in
> the maximum unsigned integer value. Consequently, the condition 'if
> (val < 16)' will still function correctly.
> 
> [1], Page size: (2^(n+12)), where 'n' is the set page size bit.
> 
> Fixes: 81720ec5320c ("usb: host: xhci: use ffs() in xhci_mem_init()")
> Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>

Actually, is it useful to fix this code if the next patch in the series
removes it completely?

I thought that you perhaps meant this simple fix to go to stable, but
it isn't marked as such.

Regards,
Michal

  reply	other threads:[~2025-03-05  8:32 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-02-04 12:41 [PATCH v3 0/2] usb: xhci: page size improvements Niklas Neronin
2025-02-04 12:41 ` [PATCH v3 1/2] usb: xhci: correct debug message page size calculation Niklas Neronin
2025-03-05  8:32   ` Michał Pecio [this message]
2025-02-04 12:41 ` [PATCH v3 2/2] usb: xhci: set page size to the xHCI-supported size Niklas Neronin
2025-02-04 16:06   ` Mathias Nyman

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