  Wind-fed high-mass X-ray binaries are powered by accretion of the radiatively
driven wind on the compact star. Accretion-generated X-rays alter the
ionization state of the wind. Because higher ionization states drive the wind
less effectively, X-ray ionization may brake acceleration of the wind. This
causes a decrease in the wind terminal velocity and mass flux in the direction
toward the X-ray source. We study the effect of X-ray ionization on the stellar
wind of B supergiants. We determine the binary parameters for which the X-ray
irradiation significantly influences the stellar wind. This can be studied in
diagrams that plot the optical depth parameter versus the X-ray luminosity. For
low optical depths or for high X-ray luminosities, X-ray ionization leads to a
disruption in the wind aimed toward the X-ray source. Observational parameters
of high-mass X-ray binaries with B-supergiant components appear outside the
wind disruption zone. The X-ray feedback determines the resulting X-ray
luminosity. For low X-ray luminosities, ionization is weak, and the wind is not
disrupted by X-rays and flows at large velocities, consequently the accretion
rate is relatively low. On the other hand, for high X-ray luminosities, the
X-ray ionization disrupts the flow braking the acceleration, the wind velocity
is low, and the accretion rate becomes high. These effects determine the X-ray
luminosity of individual binaries. Accounting for the X-ray feedback, estimated
X-ray luminosities reasonably agree with observational values. We study the
effect of small-scale wind inhomogeneities, showing that they weaken the effect
of X-ray ionization by increasing recombination and the mass-loss. This effect
is particularly important in the region of the bistability jump. We show that
ultraluminous X-ray binaries with $L_x<10^{40}$ erg/s may be powered by
accretion of a B-supergiant wind on a massive black hole.
