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phylib has some undesirable behaviour when forcing a link mode through ethtool. phylib uses this code: idx = phy_find_valid(phy_find_setting(phydev->speed, phydev->duplex), features); to find an index in the settings table. phy_find_setting() starts at index 0, and scans upwards looking for an exact speed and duplex match. When it doesn't find it, it returns MAX_NUM_SETTINGS - 1, which is 10baseT-Half duplex. phy_find_valid() then scans from the point (and effectively only checks one entry) before bailing out, returning MAX_NUM_SETTINGS - 1. phy_sanitize_settings() then sets ->speed to SPEED_10 and ->duplex to DUPLEX_HALF whether or not 10baseT-Half is supported or not. This goes against all the comments against these functions, and 10baseT-Half may not even be supported by the hardware. Rework these functions, introducing a new method of scanning the table. There are two modes of lookup that phylib wants: exact, and inexact. - in exact mode, we return either an exact match or failure - in inexact mode, we return an exact match if it exists, a match at the highest speed that is not greater than the requested speed (ignoring duplex), or failing that, the lowest supported speed, or failure. The biggest difference is that we always check whether the entry is supported before further consideration, so all unsupported entries are not considered as candidates. This results in arguably saner behaviour, better matches the comments, and is probably what users would expect. This becomes important as ethernet speeds increase, PHYs exist which do not support the 10Mbit speeds, and half-duplex is likely to become obsolete - it's already not even an option on 10Gbit and faster links. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.